department of computer science & it...jan 01, 1970 · a student may borrow some books from the...

INSTITUTE OF SOUTHERN PUNJAB (ISP)

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Department of Computer Science & IT

Laboratory Manual (A Guide to MySQL)

Prepared by: Muhammad Nouman Farooq

Senior Lecturer


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Course: Advance Database Systems (CS-214 & CS-514)

Table of Contents

Lab Activity 1- Database Design Phase (ERD) ………………………….… 3-6

Lab Activity 2- SQL Syntax, Keywords, DDL Commands ...……......….…. 7-15

Lab Activity 3- Data Manipulation Language (DML) Commands …........… 16-20

Lab Activity 4- SQL Select Statement, Where Clause & Operators …......… 21-31

Lab Activity 5- SQL Statements & Alias Syntax …………………...…....… 32-37

Lab Activity 6- SQL Union Operator, Joining & Views ………….…..….… 38-53

Lab Activity 7- Normalization up to Third Normal Form (3-NF) ..…...…..... 54-54

Lab Activity 8- SQL Aggregate Function .…..…............................................ 55-63

Lab Activities-Detailed Review- MySQL Coding using Console …..……... 64-120

Simulator Used: XAMPP Integrated Development Environment using

CONSOLE and Navicat Graphical User Interface (GUI)

Programming Language: SQL (Structured Query Language)


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Lab 1- Database Design Phase (ERD)

1. ERD Designing:

Scenarios:

1. A player plays for a cricket team. In a cricket team, at least one or more player plays.

2. Each patient has at least one or more patient histories; each instance of patient history

belongs to one patient.

3. An employee may be recorded as having many jobs; a particular job may be recorded as

having been held by many employees.

4. A person is a citizen of a country. A country has more than one citizens.

5. A student may borrow some books from the library. A book in the library must be

borrowed by a student.

6. A student takes at least one course. A course is taken by at least one student.

Case Study 1:

Odeon Cinema and other international cinemas have decided to install a centralized database.

This database should keep information regarding cinemas including its name, address and phone

number. Each CINEMA must have one or more THEATERS and each theater has a specific

SHOWING TIME. During these showing times, a MOVIE is shown to the public.


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Case Study 2:

In a school, students are allocated to different classes. Each student must be allocated to exactly

one class, and a class is formed by at least one or more than one student. Each class must be

managed by several different students on different posts, namely Monitors and Prefect. Draw an

E-R Diagram for the school, indicating Cardinalities.

2. ERD Reading:

Scenario 1:


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Scenario 2:

Scenario 3:

Scenario 4:


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Scenario 5:

Scenario 6:

End of Lab Activity 1


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Lab Activity 2 – SQL Syntax, Keywords, DDL Commands

Step No. Details of the step

1

Data Definition Language Commands: -

It is used to communicate with database. DDL is used to:

o Create an object o Alter/Modify the structure of an object

o To drop the object created.

2 The commands used are: Create, Alter, Drop, Truncate

3

Integrity Constraint: -

An integrity constraint is a mechanism used to prevent invalid data entry into

the table. It has enforcing the rules for the columns in a table. The types of the

integrity constraints are:

a) Domain Integrity b) Entity Integrity c) Referential Integrity


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4

a) Domain Integrity

This constraint sets a range and any violations that take place will prevent the

user from performing the manipulation that caused the breach. It includes:

Not Null Constraint:

While creating tables, by default the rows can have null value, the enforcement of

not null constraint in a table ensure that the table contains values.

Principle of Null Values:

o Setting null value is appropriate when the actual value is unknown, or when

a value would not be meaningful.

o A null value is not equivalent to a value of zero.

o A null value will always evaluate to null in any expression.

o When a column name is defined as not null, that column becomes a

mandatory i.e., the user must enter data into it.

o Not null Integrity constraint cannot be defined using the alter table

command when the table contain rows.

5

Check Constraint:

Check constraint can be defined to allow only a particular range of values. When

the manipulation violates this constraint, the record will be rejected. Check

condition cannot contain sub queries.


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b) Entity Integrity

Maintains uniqueness in a record. An entity represents a table and each row of

a table represents an instance of that entity. To identify each row in a table

uniquely we need to use this constraint.

There are 2 entity constraints: Unique key Constraint

It is used to ensure that information in the column for each record is unique, as

with telephone or driver’s license numbers. It prevents the duplication of value

with rows of a specified column in a set of columns’. A column defined with

the constraint can allow null value.

If unique key constraint is defined in more than one column i.e., combination

of column cannot be specified. Maximum combination of columns that a

composite unique key can contain is 16. Primary Key Constraint

A primary key avoids duplication of rows and does not allow null values. It

can be defined on one or more columns in a table and is used to uniquely

identify each row in a table. These values should never be changed and should

never be null.

A table should have only one primary key. If a primary key constraint is

assigned to more than one column or combination of column is said to be

composite primary key, which can contain 16 columns.


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c) Referential Integrity

It enforces relationship between tables. To establish parent-child relationship

between 2 tables having a common column definition, we make use of this

constraint. To implement this, we should define the column in the parent table

as primary key and same column in the child table as foreign key referring to

the corresponding parent entry. Foreign key

A column or combination of column included in the definition of

referential integrity, which would refer to a referenced key. Referenced key It is a unique or primary key upon which is defined on a column belonging to the parent table.


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SQL CREATE DATABASE Syntax

DROP DATABASE IF EXISTS `dbname`;

CREATE DATABASE IF NOT EXISTS `dbname`;

USE `dbname`;

1. Create database northwind (Import northwind database)

SQL CREATE TABLE + CONSTRAINT Syntax

Drop TABLE IF EXISTS `database_name`.`table_name`;

CREATE TABLE IF NOT EXISTS `database_name`.`table_name` ( columnName1 data_type AUTO_INCREMENT PRIMARY KEY,

columnName2 data_type(size), columnName3 data_type NOT NULL, columnName4 data_type(size) DEFAULT 'anytext', UNIQUE (columnName3), -- CONSTRAINT `uk_columnname` UNIQUE (columnName3, columnName4..)

-- PRIMARY KEY (columnName),

/* CONSTRAINT pk_columnName PRIMARY KEY (columnName1, columnName2,………) for more than one columns */

/* PRIMARY KEY (columnName1, columnName2,………) -- Or use that syntax for more than one columns */

CONSTRAINT fk_columnName FOREIGN KEY (columnName) REFERENCES ParentTableName (columnName) ON update cascade on DELETE restrict,

-- CHECK (columnName > 0),

-- CHECK (columnName = ‘text’) );


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2. Create the tables in the northwind database as per given SCHEMA Diagram


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SQL SHOW DATABASE Syntax

SHOW DATABASES

show databases

SQL SHOW TABLES Syntax

SHOW TABLES

SQL INSERT INTO Syntax

The INSERT INTO statement is used to insert new records in a table.

INSERT INTO `database_name`.`table_name`

VALUES (value1,value2,value3,...); -- comment (single line)

/*

Multi line comment

*/

Insert Data Only in Specified Columns

It is also possible to only insert data in specific columns.

INSERT INTO `database_name`.`table_name` (column1,column2,column3)

VALUES (value1,value2,value3), (value1,value2,value3) …

3. Insert any 5 rows in all the tables of northwind database.


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SQL ALTER TABLE Syntax

To add a column in a table, use the following syntax:

ALTER TABLE `database_name`.`table_name` ADD column_name datatype

To delete a column in a table, use the following syntax (notice that some database systems don't allow deleting a column):

ALTER TABLE `database_name`.`table_name` DROP COLUMN column_name

To change the data type of a column in a table, use the following syntax:

ALTER TABLE `database_name`.`table_name` MODIFY COLUMN column_name datatype

4. Practice to alter any column in any table in the northwind database.


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The DROP TABLE Syntax

The DROP TABLE statement is used to delete a table.

DROP TABLE IF EXISTS `database_name`.`table_name`

The DROP DATABASE Syntax

The DROP DATABASE statement is used to delete a database. DROP DATABASE IF EXISTS `database_name`

The TRUNCATE TABLE Syntax

What if we only want to delete the data inside the table, and not the table itself?

Then, use the TRUNCATE TABLE statement: TRUNCATE TABLE `database_name`.`table_name`

5. Drop the table CUSTOMER from the northwind database.

6. Truncate the table PRODUCT.

7. Drop the northwind database.

8. Write a code for Lab 1-Database Design Phase (ERD)



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Lab Activity 3- Data Manipulation Language (DML) Commands

Step no. Details of the step

1

DML COMMAND DML commands are the most frequently used SQL commands and is used to query

and manipulate the existing database objects. Some of the commands are: -

Insert, Select, Update and Delete

2

Insert Command

This is used to add one or more rows to a table. The values are separated by commas

and the data types char and date are enclosed in apostrophes. The values must be

entered in the same order as they are defined.

3

Select Commands

It is used to retrieve information from the table. It is generally referred to as

querying the table. We can either display all columns in a table or only specify

column from the table.

4 Update Command

It is used to alter the column values in a table. A single column may be updated or

more than one column could be updated.

5

Delete command

After inserting row in a table, we can also delete them if required. The delete

command consists of a ‘FROM’ clause followed by an optional where clause.


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The INSERT COMMAND Syntax

Inserting a single row into a table:

INSERT INTO `database_name`.`table name` VALUES (value list);

Example:

insert into customer.customer values (97, 'Nouman', '9km Bosan Road, ISP Main Campus, Multan', 'Multan', 'Punjab',

786)

Skipping the fields while inserting:

INSERT INTO database_name.tablename (column names to which data is to be

inserted) VALUES (list of values);

Note: Other way is to give null while passing the values.


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The SELECT COMMAND Syntax

Selects all rows from the table:

SELECT * FROM database_name.tablename;

Example:

SELECT * FROM customer.customer;

The retrieval of specific columns from a table: It retrieves the specified columns from the table

SELECT column_name1, …..,column_name n FROM database_name.table name;

Example:

SELECT id, name FROM customer.customer;

Elimination of duplicates from the select clause: It prevents retrieving the duplicated values. Distinct keyword is to be used.

SELECT DISTINCT col1, col2 FROM database_name.table name;

Example:

SELECT DISTINCT name FROM customer.customer;


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Select command with where clause: To select specific rows from a table we include “WHERE” clause in the select command. It

can appear only after the “FROM” clause.

SELECT column_name1, …..,column_name n FROM database_name.table name WHERE condition;

Example:

SELECT name FROM customer.customer WHERE id = 95;

Select command with order by clause: SELECT column_name1, …..,column_name n FROM database_name.table name

WHERE condition ORDER BY colmnname;

Example:

SELECT name FROM customer.customer ORDER BY id;

SELECT name FROM customer.customer ORDER BY id ASC;

SELECT name FROM customer.customer ORDER BY id Desc;

Select command to create a table (Inserting Existing Table Records): CREATE TABLE if not exists database_name.tablename AS SELECT * FROM

existing_tablename;

Example:

CREATE TABLE customer.customer1 AS SELECT * FROM

customer.customer;

Select command to insert records: INSERT INTO database_name.tablename (SELECT columns FROM existing_tablename);


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Example:

INSERT INTO customer.customer1 (SELECT * FROM customer.customer);

The UPDATE COMMAND Syntax: update database_name.tablename SET FIELD = values WHERE condition;

Example:

UPDATE customer.customer1 SET name = 'Arslan' WHERE id = 97;

The DELETE COMMAND Syntax:

DELETE FROM database_name.tablename WHERE conditions;

Example:

DELETE FROM customer.customer1 WHERE ID = 98;

1. Import CUSTOMER database (CUSTOMER database for lab activity 3) and

Insert your meaningful record into Customer table

2. Select customer id, name from the customer table

3. CREATE CUSTOMER1 table using above syntax & UPDATE the customer1

table to set the state to NY of all customer ranging from ID 1 to 10

4. Delete only those who are living in state NY

5. List the records in the CUSTOMER table order by ID into descending order

6. Display only that customer whose ID is from 25 to 30

7. Display STATE from the table CUSTOMER avoiding the duplicated values.



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Lab Activity 4- SQL Select Statement, Where Clause & Operators

The SQL SELECT Statement

The SELECT statement is used to select data from a database.

The result is stored in a result table, called the result-set.

SQL SELECT Syntax

To select the specific data

SELECT column_name,column_name

FROM database_name.table_name

To select the entire data in a table

SELECT * FROM database_name.table_name

1. Import CUSTOMER database (CUSTOMER database for lab activity 4) and Find

the "CustomerName" and "City" columns from the "Customer" table.

2. Find all the columns from the "Customer" table

The SQL SELECT DISTINCT Statement

In a table, a column may contain many duplicate values; and sometimes you only want to list the

different (distinct) values. The DISTINCT keyword can be used to return only distinct (different)

values.

SQL SELECT DISTINCT Syntax SELECT DISTINCT column_name,column_name


3. Find only the distinct values from the "City" columns from the "Customer" table


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The SQL WHERE Clause

The WHERE clause is used to filter records. The WHERE clause is used to extract only those

records that fulfill a specified criterion.

SQL WHERE Syntax SELECT column_name,column_name


WHERE column_name value

4. Find all the customer from the city "New York", in the "Customer" table.

5. Find all the customer in the customer tables whose CustomerID=1.


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Operators in the WHERE Clause

The following operators can be used in the WHERE clause:

Operator Description

= Equal

<> Not equal. Note: In some versions of SQL this operator may be written as !=

> Greater than

< Less than

>= Greater than or equal

<= Less than or equal

BETWEEN Between an inclusive range

LIKE Search for a pattern

IN To specify multiple possible values for a column


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The SQL LIKE Operator

The LIKE operator is used to search for a specified pattern in a column.

SQL LIKE Syntax SELECT column_name(s)


WHERE column_name LIKE pattern

SELECT * FROM table_name

WHERE column_name LIKE pattern

SQL LIKE Operator Examples

The following SQL statement selects all customers with a City starting with the letter "s":

Try it yourself SELECT * FROM customer.customer

WHERE City LIKE 's%';

Tip: The "%" sign is used to define wildcards (missing letters) both before and after the pattern.

The following SQL statement selects all customers with a City ending with the letter "s":


WHERE City LIKE '%s'

The following SQL statement selects all customer with a Country containing the pattern "land":


WHERE city LIKE '%land%'


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Using the NOT keyword allows you to select records that do NOT match the pattern.

The following SQL statement selects all customer with Country NOT containing the pattern "land":


WHERE city NOT LIKE '%land%'

SQL Wildcard Characters

In SQL, wildcard characters are used with the SQL LIKE operator. SQL wildcards are used to search

for data within a table. With SQL, the wildcards are:

Wildcard Description

% A substitute for zero or more characters

_ A substitute for a single character

[charlist] Sets and ranges of characters to match

[^charlist]

or

[!charlist]

Matches only a character NOT specified within the brackets


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Using the SQL % Wildcard

The following SQL statement selects all customer with a City starting with "b":


WHERE City LIKE 'b%'

The following SQL statement selects all customer with a City containing the pattern "es":


WHERE City LIKE '%es%'

Using the SQL _ Wildcard

The following SQL statement selects all customer with a City starting with any character, followed

by "oston":


WHERE City LIKE '_oston'

The following SQL statement selects all customer with a City starting with "L", followed by any

character, followed by "s", followed by any character, followed by "Vegas":


WHERE City LIKE 'L_s_Vegas'


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Using the SQL [charlist] Wildcard

The following SQL statement selects all customer with a City starting with "l", "a", or "s":


WHERE City LIKE 'LAS%'

The following SQL statement selects all customer with a City starting with "holl":


WHERE City LIKE 'holl%'

The following SQL statement selects all customer with a City NOT starting with "h", “o", “l", or "l":

Try it yourself

SELECT * FROM customer.customer

WHERE City NOT LIKE 'holl%'


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The IN Operator

The IN operator allows you to specify multiple values in a WHERE clause.

SQL IN Syntax SELECT column_name(s)


WHERE column_name IN (value1,value2,...)

IN Operator Example

The following SQL statement selects all customer with a City of "Paris" or "London":


WHERE City IN ('Paris','London')


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The SQL BETWEEN Operator

The BETWEEN operator selects values within a range. The values can be numbers, text, or dates.

SQL BETWEEN Syntax

SELECT column_name(s)


WHERE column_name BETWEEN value1 AND value2

SQL NOT BETWEEN Syntax



WHERE column_name NOT BETWEEN value1 AND value2

6. Find all addresses with a id BETWEEN 15 and 25.

7. Display the addresses outside the range of 15 and 25, use NOT BETWEEN

BETWEEN Operator with IN Example

The following SQL statement selects all customer with a Id BETWEEN 1 and 20, but customer with a

id of 1, 2, or 3 should not be displayed:


WHERE (id BETWEEN 1 AND 10)

AND NOT id IN (1,2,3)


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BETWEEN Operator with Text Value Example

The following SQL statement selects all customer with a city beginning with any of the letter

BETWEEN 'D' and 'I':


WHERE city BETWEEN 'D' AND 'I'

NOT BETWEEN Operator with Text Value Example

The following SQL statement selects all customer with a city beginning with any of the letter NOT

BETWEEN 'D' and 'I':


WHERE city NOT BETWEEN 'D' AND 'I'

BETWEEN Operator with Date Value Example

The following SQL statement selects all customer with an zip BETWEEN '2104' and '3320':


WHERE zip BETWEEN 2104 AND 3320


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Notice that the BETWEEN operator can produce different result in different databases!

In some databases, BETWEEN selects fields that are between and excluding the test values.

In other databases, BETWEEN selects fields that are between and including the test values.

And in other databases, BETWEEN selects fields between the test values, including the first test

value and excluding the last test value.

Therefore: Check how your database treats the BETWEEN operator!

8. Practice and Display every given above Syntax in Customer Table



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Lab Activity 5- SQL Statements & Alias Syntax

The SQL AND & OR Operators

The AND & OR operators are used to filter records based on more than one condition.

The AND operator displays a record if both the first condition AND the second condition are

true.

The OR operator displays a record if either the first condition OR the second condition is true.

SQL AND Syntax


WHERE column_name=value

AND column_name=value

SQL OR Syntax


WHERE column_name=value

OR column_name=value

1. Find all customers from the country "Germany" AND the city "Berlin", in the "Customers"

table.

2. Find all customers from the city "Berlin" OR "München", in the "Customers" table.


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Combining AND & OR

You can also combine AND and OR (use parenthesis to form complex expressions).

The following SQL statement selects all customers from the country "Germany" AND the city must

be equal to "Berlin" OR "München", in the "Customers" table:

Try it yourself

SELECT * FROM customer.Customer

WHERE Country='Germany'

AND (City='Berlin' OR City='München')

The SQL ORDER BY Keyword

The ORDER BY keyword is used to sort the result-set by one or more columns.

The ORDER BY keyword sorts the records in ascending order by default. To sort the records in a

descending order, you can use the DESC keyword.

SQL ORDER BY Syntax

SELECT column_name, column_name


ORDER BY column_name ASC|DESC, column_name ASC|DESC

3. Find all customers from the "Customers" table, sorted by the "Country" column.

4. Find all customers from the "Customers" table, sorted DESCENDING by the "Country"

column.

5. Find all customers from the "Customers" table, sorted by the "Country" and the

"CustomerName" column.

6. Find all customers from the "Customers" table, sorted ascending by the "Country" and

descending by the "CustomerName" column


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The SQL UPDATE Statement

The UPDATE statement is used to update existing records in a table.

SQL UPDATE Syntax

UPDATE database_name.table_name

SET column1=value1,column2=value2,...

WHERE some_column=some_value

Notice the WHERE clause in the SQL UPDATE statement!

The WHERE clause specifies which record or records that should be updated. If you omit the

WHERE clause, all records will be updated!

7. Update the customer "Alfreds Futterkiste" with a new contact person and city.

The SQL DELETE Statement

The DELETE statement is used to delete rows in a table.

SQL DELETE Syntax

DELETE FROM database_name.table_name

WHERE some_column=some_value

Notice the WHERE clause in the SQL DELETE statement!

The WHERE clause specifies which record or records that should be deleted. If you omit the

WHERE clause, all records will be deleted!

8. Delete the customer "Alfreds Futterkiste" from the "Customers" table


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The SQL LIMIT Clause

The LIMIT clause is used to specify the number of records to return.

The LIMIT clause can be very useful on large tables with thousands of records. Returning a large

number of records can impact on performance.

Note: Not all database systems support the LIMIT clause.

MySQL LIMIT Syntax



LIMIT number

9. Find the two first records from the "Customers" table.


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SQL Aliases

SQL aliases are used to give a database table, or a column in a table, a temporary name.

Basically, aliases are created to make column names more readable.

SQL Alias Syntax for Columns

SELECT column_name AS alias_name


SQL Alias Syntax for Tables


FROM database_name.table_name AS alias_name

Alias Example for Table Columns

The following SQL statement specifies two aliases, one for the CustomerName column and one for

the ContactName column.

Tip: It requires double quotation marks or square brackets if the column name contains spaces:

Try it yourself SELECT CustomerName AS Customer, ContactName AS [Contact Person]

FROM Customers

In the following SQL statement, we combine four columns (Address, City, PostalCode, and Country)

and create an alias named "Address":

Try it yourself

SELECT CustomerName, CONCAT (Address,', ',City,', ',PostalCode,', ',Country) AS Address

FROM Customers


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Alias Example for Tables The following SQL statement selects all the orders from the customer with CustomerID=4 (Around

the Horn). We use the "Customers" and "Orders" tables, and give them the table aliases of "c" and

"o" respectively (Here we have used aliases to make the SQL shorter):

Try it yourself SELECT o.OrderID, o.OrderDate, c.CustomerName

FROM customer.Customer AS c, Orders AS o

WHERE c.CustomerName="Around the Horn"

AND c.CustomerID=o.CustomerID

The same SQL statement without aliases:

Try it yourself SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName

FROM customer.Customer, Orders

WHERE Customer.CustomerName="Around the Horn"

AND Customer.CustomerID=Orders.CustomerID

Aliases can be useful when:

• There are more than one table involved in a query

• Functions are used in the query

• Column names are big or not very readable

• Two or more columns are combined together



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Lab Activity 6- SQL Union Operator, Joining & Views

SQL JOIN An SQL JOIN clause is used to combine rows from two or more tables, based on a common field

between them.

Different SQL JOINs

• CROSS JOIN: Cross Join returns the Cartesian product of rows from tables in the join.

• INNER JOIN: Returns all rows when there is at least one match in BOTH tables

• LEFT JOIN: Return all rows from the left table, and the matched rows from the right

table

• RIGHT JOIN: Return all rows from the right table, and the matched rows from the left

table

• FULL JOIN: Return all rows when there is a match in ONE of the tables


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SQL CROSS JOIN Keyword

Cross Join returns the Cartesian product of rows from tables in the join.

SQL CROSS JOIN Syntax SELECT column_name(s)

FROM database_name.table1

CROSS JOIN database_name.table2

ORDER BY `CROS`.`table_name that will be in both table’s` ASC -- Example of an Explicit Cross Join

OR

SELECT *

FROM database_name.table1 . database_name.table2

ORDER BY `database_name`.`table_name that will be in both table’s` ASC -- Example of an Implicit

Cross Join

Try it yourself

SELECT * from JOINING.EMPLOYEE

CROS JOIN

JOINING.Department

ORDER BY `CROS`.`DepartmentID` ASC -- Example of an Explicit Cross Join

SELECT * from `JOINING`.`EMPLOYEE` , `JOINING`.`Department` ORDER BY

`EMPLOYEE`.`DepartmentID` ASC; -- Example of an Implicit Cross Join

http://localhost/phpmyadmin/url.php?url=http://dev.mysql.com/doc/refman/5.5/en/select.html


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SQL INNER JOIN Keyword The INNER JOIN keyword selects all rows from both tables as long as there is a match between the

columns in both tables.

SQL INNER JOIN Syntax SELECT column_name(s)

FROM table1

INNER JOIN table2

ON table1.column_name=table2.column_name

OR


FROM table1

JOIN table2


PS! INNER JOIN is the same as JOIN.

SQL INNER JOIN Example

The following SQL statement will return all customers with orders:

Try it yourself SELECT Customers.CustomerName, Orders.OrderID

FROM Customers

INNER JOIN Orders

ON Customers.CustomerID=Orders.CustomerID

ORDER BY Customers.CustomerName

Note: The INNER JOIN keyword selects all rows from both tables as long as there is a match between

the columns. If there are rows in the "Customers" table that do not have matches in "Orders", these

customers will NOT be listed.


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SQL LEFT JOIN Keyword The LEFT JOIN keyword returns all rows from the left table (table1), with the matching rows in the

right table (table2). The result is NULL in the right side when there is no match.

SQL LEFT JOIN Syntax


FROM table1

LEFT JOIN table2


OR


FROM table1

LEFT OUTER JOIN table2


PS! In some databases LEFT JOIN is called LEFT OUTER JOIN.

SQL LEFT JOIN Example

The following SQL statement will return all customers, and any orders they might have:

Try it yourself SELECT Customers.CustomerName, Orders.OrderID

FROM Customers

LEFT JOIN Orders


ORDER BY Customers.CustomerName

Note: The LEFT JOIN keyword returns all the rows from the left table (Customers), even if there are

no matches in the right table (Orders).


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SQL RIGHT JOIN Keyword

The RIGHT JOIN keyword returns all rows from the right table (table2), with the matching rows in

the left table (table1). The result is NULL in the left side when there is no match.

SQL RIGHT JOIN Syntax


FROM table1

RIGHT JOIN table2


OR


FROM table1

RIGHT OUTER JOIN table2


PS! In some databases, RIGHT JOIN is called RIGHT OUTER JOIN.

SQL RIGHT JOIN Example

The following SQL statement will return all employees, and any orders they have placed:

Try it yourself SELECT Orders.OrderID, Employees.FirstName

FROM Orders

RIGHT JOIN Employees

ON Orders.EmployeeID=Employees.EmployeeID

ORDER BY Orders.OrderID

Note: The RIGHT JOIN keyword returns all the rows from the right table (Employees), even if there

are no matches in the left table (Orders).


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SQL FULL OUTER JOIN Keyword

The FULL OUTER JOIN keyword returns all rows from the left table (table1) and from the right table

(table2). The FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.

Important Note: We don't have FULL JOINS on MySQL, but we can sure use this query to get our

desired result as per full join definition.

SQL FULL OUTER JOIN Syntax

SELECT * FROM t1 -- Syntax with Two Tables “t1 and t2”

LEFT JOIN t2 ON t1.column_name = t2.column_name

UNION ALL

SELECT * FROM t1

RIGHT JOIN t2 ON t1.column_name = t2.column_name

SQL FULL OUTER JOIN Example

The following SQL statement selects all customers, and all orders: SELECT * from `JOINING`.ÈMPLOYEE`

LEFT JOIN `JOINING`.`DEPARTMENT`

ON ÈMPLOYEE`.`DEPARTMENTID` = `DEPARTMENT`.`DEPARTMENTID`

UNION ALL

SELECT * FROM `JOINING`.ÈMPLOYEE`

RIGHT JOIN

ON ÈMPLOYEE`.`DEPARTMENTID` = `DEPARTMENT`.`DEPARTMENTID`

ORDER BY `DEPARTMENT`.`DEPARTMENTID` ASC;

Note: The FULL OUTER JOIN keyword returns all the rows from the left table (Customers), and all

the rows from the right table (Orders). If there are rows in "Customers" that do not have matches in

"Orders", or if there are rows in "Orders" that do not have matches in "Customers", those rows will

be listed as well.


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Lab Assignment: -

1. Create three tables named EMPLOYEE_DETAIL & SALARY & PHONE_NUMBER in a

database named EMPLOYEE via code as shown in figure:

2. Implement all Joining Queries on the above created database named EMPLOYEE_DETAIL


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The SQL UNION Operator

The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns. The

columns must also have similar data types. Also, the columns in each SELECT statement must be in

the same order.

SQL UNION Syntax

SELECT column_name(s) FROM table1

UNION


Note: The UNION operator selects only distinct values by default. To allow duplicate values, use the

ALL keyword with UNION.

SQL UNION ALL Syntax


UNION ALL


PS: The column names in the result-set of a UNION are usually equal to the column names in the

first SELECT statement in the UNION.


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SQL UNION Example

The following SQL statement selects all the different cities (only distinct values) from the

"Customers" and the "Suppliers" tables:

Try it yourself SELECT City FROM Customers

UNION

SELECT City FROM Suppliers

ORDER BY City

Note: UNION cannot be used to list ALL cities from the two tables. If several customers and

suppliers share the same city, each city will only be listed once. UNION selects only distinct values.

Use UNION ALL to also select duplicate values!

SQL UNION ALL Example

The following SQL statement uses UNION ALL to select all (duplicate values also) cities from the

"Customers" and "Suppliers" tables:

Try it yourself SELECT City FROM Customers

UNION ALL

SELECT City FROM Suppliers

ORDER BY City


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SQL UNION ALL With WHERE

The following SQL statement uses UNION ALL to select all (duplicate values also) German cities

from the "Customers" and "Suppliers" tables:

Try it yourself SELECT City, Country FROM Customers


UNION ALL

SELECT City, Country FROM Suppliers


ORDER BY City


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The SQL SELECT INTO Statement

The SELECT INTO statement selects data from one table and inserts it into a new table.

SQL SELECT INTO Syntax

We can copy all columns into the new table: SELECT *

INTO newtable [IN externaldb]

FROM table1

Or we can copy only the columns we want into the new table: SELECT column_name(s)

INTO newtable [IN externaldb]

FROM table1

The new table will be created with the column-names and types as defined in the SELECT

statement. You can apply new names using the AS clause.

SQL SELECT INTO Examples

• Create a backup copy of Customers: SELECT *

INTO CustomersBackup2013

FROM Customers

• Use the IN clause to copy the table into another database: SELECT *

INTO CustomersBackup2013 IN 'Backup.mdb'

FROM Customers

• Copy only a few columns into the new table: SELECT CustomerName, ContactName


FROM Customers


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• Copy only the German customers into the new table: SELECT *


FROM Customers


• Copy data from more than one table into the new table: SELECT Customers.CustomerName, Orders.OrderID

INTO CustomersOrderBackup2013

FROM Customers

LEFT JOIN Orders


Tip: The SELECT INTO statement can also be used to create a new, empty table using the schema of

another. Just add a WHERE clause that causes the query to return no data: SELECT *

INTO newtable

FROM table1

WHERE 1=0


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The SQL INSERT INTO SELECT Statement

The INSERT INTO SELECT statement selects data from one table and inserts it into an existing table.

Any existing rows in the target table are unaffected.

SQL INSERT INTO SELECT Syntax

We can copy all columns from one table to another, existing table: INSERT INTO table2

SELECT * FROM table1

Or we can copy only the columns we want to into another, existing table: INSERT INTO table2

(column_name(s))


FROM table1

SQL INSERT INTO SELECT Examples

Copy only a few columns from "Suppliers" into "Customers":

Try it yourself INSERT INTO Customers (CustomerName, Country)

SELECT SupplierName, Country FROM Suppliers

Copy only the German suppliers into "Customers":

Try it yourself INSERT INTO Customers (CustomerName, Country)

SELECT SupplierName, Country FROM Suppliers



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SQL CREATE VIEW Statement

In SQL, a view is a virtual table based on the result-set of an SQL statement.

A view contains rows and columns, just like a real table. The fields in a view are fields from one or

more real tables in the database.

You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the

data were coming from one single table.

SQL CREATE VIEW Syntax

CREATE VIEW view_name AS


FROM table_name

WHERE condition

Note: A view always shows up-to-date data! The database engine recreates the data, using the

view's SQL statement, every time a user queries a view

SQL CREATE VIEW Examples

If you have the Northwind database, you can see that it has several views installed by default.

• The view "Current Product List" lists all active products (products that are not discontinued)

from the "Products" table. The view is created with the following SQL: CREATE VIEW [Current Product List] AS

SELECT ProductID,ProductName

FROM Products

WHERE Discontinued=No


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We can query the view above as follows: SELECT * FROM [Current Product List]

• Another view in the Northwind sample database selects every product in the "Products"

table with a unit price higher than the average unit price:

CREATE VIEW [Products Above Average Price] AS

SELECT ProductName,UnitPrice

FROM Products

WHERE UnitPrice>(SELECT AVG(UnitPrice) FROM Products)

We can query the view above as follows: SELECT * FROM [Products Above Average Price]

• Another view in the Northwind database calculates the total sale for each category in 1997.

Note that this view selects its data from another view called "Product Sales for 1997":

CREATE VIEW [Category Sales For 1997] AS

SELECT DISTINCT CategoryName,Sum(ProductSales) AS CategorySales

FROM [Product Sales for 1997]

GROUP BY CategoryName

We can query the view above as follows: SELECT * FROM [Category Sales For 1997]

We can also add a condition to the query. Now we want to see the total sale only for the category

"Beverages":

SELECT * FROM [Category Sales For 1997]

WHERE CategoryName='Beverages'


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SQL Updating a View

You can update a view by using the following syntax:

SQL CREATE OR REPLACE VIEW Syntax

CREATE OR REPLACE VIEW view_name AS


FROM table_name

WHERE condition

Now we want to add the "Category" column to the "Current Product List" view. We will update the

view with the following SQL: CREATE OR REPLACE VIEW [Current Product List] AS

SELECT ProductID,ProductName,Category

FROM Products

WHERE Discontinued=No

SQL Dropping a View

You can delete a view with the DROP VIEW command.

SQL DROP VIEW Syntax

DROP VIEW view_name



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Lab Activity 7- Normalization up to Third Normal Form (3-NF)

Database Normalization up to 3-NF:

Lab Assignment: -

1. Create and Normalize the following given table’s up to 3-NF via Code:

2. Name of a database must be ADVISOR_SCHEDULE



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Lab Activity 8- SQL Aggregate Functions

SQL Aggregate Functions

SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

• AVG() - Returns the average value

• COUNT() - Returns the number of rows

• FIRST() - Returns the first value

• LAST() - Returns the last value

• MAX() - Returns the largest value

• MIN() - Returns the smallest value

• SUM() - Returns the sum

•

SQL Scalar functions

SQL scalar functions return a single value, based on the input value.

Useful scalar functions:

• UCASE() - Converts a field to upper case

• LCASE() - Converts a field to lower case

• MID() - Extract characters from a text field

• LEN() - Returns the length of a text field

• ROUND() - Rounds a numeric field to the number of decimals specified

• NOW() - Returns the current system date and time

• FORMAT() - Formats how a field is to be displayed


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The AVG() Function

The AVG() function returns the average value of a numeric column.

SQL AVG() Syntax

SELECT AVG(column_name) FROM table_name

SQL AVG() Example

The following SQL statement gets the average value of the "Price" column from the "Products"

table:

Try it yourself SELECT AVG(Price) AS PriceAverage FROM Products

The following SQL statement selects the "ProductName" and "Price" records that have an above

average price:

Try it yourself SELECT ProductName, Price FROM Products

WHERE Price>(SELECT AVG(Price) FROM Products)

SQL COUNT() Function

The COUNT() function returns the number of rows that matches a specified criteria.

SQL COUNT(column_name) Syntax

The COUNT(column_name) function returns the number of values (NULL values will not be counted)

of the specified column: SELECT COUNT(column_name) FROM table_name

SQL COUNT(*) Syntax

The COUNT(*) function returns the number of records in a table: SELECT COUNT(*) FROM table_name


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SQL COUNT(DISTINCT column_name) Syntax

The COUNT(DISTINCT column_name) function returns the number of distinct values of the specified

column: SELECT COUNT(DISTINCT column_name) FROM table_name

Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but not with Microsoft

Access.

SQL COUNT(column_name) Example

The following SQL statement counts the number of orders from "CustomerID"=7 from the "Orders"

table:

Try it yourself SELECT COUNT(CustomerID) AS OrdersFromCustomerID7 FROM Orders

WHERE CustomerID=7

SQL COUNT(*) Example

The following SQL statement counts the total number of orders in the "Orders" table:

Try it yourself SELECT COUNT(*) AS NumberOfOrders FROM Orders

SQL COUNT(DISTINCT column_name) Example

The following SQL statement counts the number of unique customers in the "Orders" table:

Try it yourself SELECT COUNT(DISTINCT CustomerID) AS NumberOfCustomers FROM Orders


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The MAX() Function

The MAX() function returns the largest value of the selected column.

SQL MAX() Syntax

SELECT MAX(column_name) FROM table_name

SQL MAX() Example

The following SQL statement gets the largest value of the "Price" column from the "Products" table:

Try it yourself SELECT MAX(Price) AS HighestPrice FROM Products

The MIN() Function

The MIN() function returns the smallest value of the selected column.

SQL MIN() Syntax

SELECT MIN(column_name) FROM table_name

SQL MIN() Example

The following SQL statement gets the smallest value of the "Price" column from the "Products"

table:

Try it yourself SELECT MIN(Price) AS SmallestOrderPrice FROM Products

The SUM() Function

The SUM() function returns the total sum of a numeric column.

SQL SUM() Syntax

SELECT SUM(column_name) FROM table_name

SQL SUM() Example

The following SQL statement finds the sum of all the "Quantity" fields for the "OrderDetails" table:

Try it yourself SELECT SUM(Quantity) AS TotalItemsOrdered FROM OrderDetails


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The GROUP BY Statement

The GROUP BY statement is used in conjunction with the aggregate functions to group the result-

set by one or more columns.

SQL GROUP BY Syntax

SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE column_name operator value

GROUP BY column_name

SQL GROUP BY Example Now we want to find the number of orders sent by each shipper.

The following SQL statement counts as orders grouped by shippers:

Try it yourself SELECT Shippers.ShipperName,COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders

LEFT JOIN Shippers

ON Orders.ShipperID=Shippers.ShipperID

GROUP BY ShipperName

GROUP BY More Than One Column

We can also use the GROUP BY statement on more than one column, like this:

Try it yourself SELECT Shippers.ShipperName, Employees.LastName,

COUNT(Orders.OrderID) AS NumberOfOrders

FROM ((Orders

INNER JOIN Shippers

ON Orders.ShipperID=Shippers.ShipperID)

INNER JOIN Employees

ON Orders.EmployeeID=Employees.EmployeeID)

GROUP BY ShipperName,LastName


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The HAVING Clause

The HAVING clause was added to SQL because the WHERE keyword could not be used with

aggregate functions.

SQL HAVING Syntax

SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE column_name operator value

GROUP BY column_name

HAVING aggregate_function(column_name) operator value

SQL HAVING Example

Now we want to find if any of the employees has registered more than 10 orders.

We use the following SQL statement:

Try it yourself SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders FROM (Orders


ON Orders.EmployeeID=Employees.EmployeeID)

GROUP BY LastName

HAVING COUNT(Orders.OrderID) > 10

Now we want to find if the employees "Davolio" or "Fuller" have registered more than 25 orders.

We add an ordinary WHERE clause to the SQL statement:

Try it yourself SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders


ON Orders.EmployeeID=Employees.EmployeeID

WHERE LastName='Davolio' OR LastName='Fuller'

GROUP BY LastName

HAVING COUNT(Orders.OrderID) > 25


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The UPPER() Function

The UPPER() function converts the value of a field to uppercase.

SQL UPPER Syntax

SELECT UPPER(column_name) FROM table_name

SQL UPPER() Example

The following SQL statement selects the "CustomerName" and "City" columns from the

"Customers" table, and converts the "CustomerName" column to uppercase:

Try it yourself SELECT UPPER(CustomerName) AS Customer, City

FROM Customers

The LOWER() Function

The LOWER() function converts the value of a field to lowercase.

SQL LOWER() Syntax

SELECT LOWER(column_name) FROM table_name

SQL LOWER() Example

The following SQL statement selects the "CustomerName" and "City" columns from the

"Customers" table, and converts the "CustomerName" column to lowercase:

Try it yourself SELECT LOWER(CustomerName) AS Customer, City

FROM Customers


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The LEN() Function

The LEN() function returns the length of the value in a text field.

SQL LEN() Syntax

SELECT LEN(column_name) FROM table_name

SQL LEN() Example

The following SQL statement selects the "CustomerName" and the length of the values in the

"Address" column from the "Customers" table:

Try it yourself SELECT CustomerName,LEN(Address) as LengthOfAddress

FROM Customers

The ROUND() Function

The ROUND() function is used to round a numeric field to the number of decimals specified.

Note: Many database systems do rounding differently than you might expect. When rounding a

number with a fractional part to an integer, our school teachers told us to round .1 through .4

DOWN to the next lower integer, and .5 through .9 UP to the next higher integer. But if all the digits

1 through 9 are equally likely, this introduces a slight bias towards infinity, since we always round .5

up. Many database systems have adopted the IEEE 754 standard for arithmetic operations,

according to which the default rounding behavior is "round half to even." In this scheme, .5 is

rounded to the nearest even integer. So, both 11.5 and 12.5 would be rounded to 12.

SQL ROUND() Syntax

SELECT ROUND(column_name,decimals) FROM table_name

Parameter Description

column_name Required. The field to round.

decimals Required. Specifies the number of decimals to be returned.


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SQL ROUND() Example

The following SQL statement selects the product name and rounds the price in the "Products" table:

Try it yourself SELECT ProductName, ROUND(Price,0) AS RoundedPrice

FROM Products

The NOW() Function

The NOW() function returns the current system date and time.

SQL NOW() Syntax

SELECT NOW() FROM table_name

SQL NOW() Example

The following SQL statement selects the product name, and price for today from the "Products"

table:

Try it yourself SELECT ProductName, Price, Now() AS PerDate

FROM Products



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Lab Activities Detailed Review- MySQL Coding Using Console

XAMPP: -

XAMPP stands for Cross-Platform (X), Apache (A), MySQL (M), PHP

(P) and Perl (P). It is a simple, light-weighted Apache server that makes it

extremely easy for developers to create a local http server with just few clicks.

An integrated development environment (IDE) is a software application that

provides comprehensive facilities to computer programmers for software

development. An IDE normally consists of a source code editor, build automation

tools and a debugger/Tester of Program/Execution of program.

After Installation of XAMPP Server

Starting Services of Apache and MySQL (the sign changes from red to green): -


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We can access the local server via graphical user interface (GUI) by click on

the Admin button of MySQL.

phpMyAdmin: -

It is a free and open source tool/simulator written in PHP intended

to handle the administration of MySQL or MariaDB (DBMS Engines) with the use

of a web browser. It can perform various tasks such as creating, modifying or

deleting databases, tables, fields or rows; executing SQL statements; or managing

users and permissions.

Apache: -

It is the most widely used web server software. Developed and

maintained by Apache Software Foundation, Apache is an open source software

available for free. It runs on 67% of all webservers in the world. It is fast, reliable,

and secure.


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We can access the local server via Domain Name directly in the browser that is by default (after

starting services of Apache and MySQL): -

localhost/phpmyadmin

Also, we can access the local server via loopback IP Address in web browser

that is by default (after starting services of Apache and MySQL): -


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127.0.0.1/phpmyadmin

127.0.0.1: -


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This is a loopback IP address (Special IP address) that is used to

access the local server.

Drop Command: -

This command is disable by default. So, to enable it follow the

following process:

1. Go To: -

C:\xampp\phpmyadmin\libraries

2. Open the file called "config.default.php"

3. Go to line 653 and change $cfg['AllowUserDropDatabase'] = false; to true

4. Restart the server to see the changes

Securing Server ROOT USER by Implementing Password using the following

steps: -

Go into Edit Privileges


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Then, Go into Change Password: -


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Than: -


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Go into installed directory of XAMPP:

C:\xampp\phpMyAdmin

Open: config.inc

And Change: -

config to cookie

Then, Change and Type that password that already assigned in Server: -


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Data Definition Language Commands (DDL Commands): -


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1. CREATE

2. ALTER

3. DROP

4. TRUNCATE

Data Manipulation Language Commands (DML Commands): -

1. INSERT

2. SELECT

3. UPDATE

4. DELETE

SQL Keywords: -

1. MODIFY

2. SHOW

3. USE

SQL (Sequel) is Case Insensitive

SQL (Sequel) is Open Source Language that means FREE FOR ALL


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Double Hyphen -- is used for single line comment

/*

these backslash steric and steric backslash is used for multi-line comment

*/

# is NOT a standard SQL Comment

; -- semi colon is used to terminate a query)

/* When we write a single SQL Query than we may not terminate it using

Semi Colon “;” */

Conditions: these given below conditions are used to make any query in

MySQL error free and efficient

IF EXISTS and IF NOT EXISTS

Identifier: - `


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In MySQL, an Identifier is used to separate database and table name.

Identifier is a sequence of characters used to identify or refer to a program or an

element, such as a variable or a set of data, within it.

`Database_Name`

/* Advantage of Using Identifier in MySQL Coding: Identifier is a sequence of

characters used to identify or refer to a program or an element, such as a variable

or a set of data, within it for Example If we want to create a Database with the

name “CREATE”. We cannot create it without the use of an Identifier because

CREATE is a Command in MySQL. */

-- Example: - "The following Command cannot be executed without

Identifier"

/* drop database if exists `create`; CREATE DATABASE IF NOT EXISTS

CREATE; */

/* But; Example: - "The following Command can be executed with Identifier" */

drop database if exists `create`; CREATE DATABASE IF NOT EXISTS

`CREATE`;

Qualifier Character: - .

In MySQL the Qualifier Character is a separate token and need not be connecting

with the associated identifiers. For example,

`table_name`.`column_name` and `table_name` . `column_name` are

equivalen

-- Without Selecting any database, we can also run some Queries: -


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select 25 + 25; -- We can perform calculations in Console/Command line Interface

(CLI)

select 50 + 25; -- We can perform calculations in Console/CLI

select 26 mod 26; -- We can perform calculations in Console/CLI

select 27 mod 26; -- We can perform calculations in Console/CLI

select "This is Database Systems lab "; -- We can write and show output in

Console/CLI

select "HELLO CLASS!!"; -- We can write and show output in Console/CLI

select "this subject is just amazing"; -- We can write and show output in

Console/CLI

SELECT SYSDATE(); -- SYSDATE() Function returns current date & time of

the system

Show Databases; -- To show all databases in a Server

-- Use database_Name -- Syntax to use a specific database


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drop database if exists `LAB`; -- Use IF EXISTS to prevent an error from

occurring for databases that do not exist

create database `LAB`; -- Creating a database VIA Single Query (Double

Hyphen for Comments)

use `lab`;

create table `lab`.`TEST`

(

`testNo` int (3) not null auto_increment,

`testId` int(3),

`testName` varchar (20),

`CREATE` int (20), -- If we want to Create a CREATE TABLE we must use

identifier

primary key (`testNo`, `testId`, `testName`) /* To create multiple primary

keys (Composite Primary Key in a table; Use the given syntax) */

);

/*

The DESCRIBE and EXPLAIN statements are synonyms, used either to obtain

information about table structure via code.

*/

DESCRIBE `lab`.`test`; -- to show the structure of a table

drop database `LAB`; -- To delete a Database

https://dev.mysql.com/doc/refman/5.7/en/describe.html

https://dev.mysql.com/doc/refman/5.7/en/explain.html


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create database IF NOT EXISTS `LAB`; -- Creating a database VIA Single but

efficient Query

drop database if exists `LAB`; -- To delete a Database Query but Efficient than

previous query

drop database if exists `lab1`; -- To delete a Database Query

create database if not exists `LAB1`; /* Creating, Selecting and Inserting

Values in Table VIA Single Query (Double Hyphen for Comments) */

use `lab1`;

create table `lab1`.`TEST` /* Using Qualifier Character to quickly

create a table in a selected database via single query */

(

`testId` int(2) not null PRIMARY KEY,

`test1Id` int(2),

`testName` varchar (20)

);

create table `lab1`.`TEST1`

(

`test1Id` int(2),

`testId` int(2),


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`test1Name` varchar (20),

constraint `fk_1` FOREIGN KEY (`testId`) references `lab1`.`test` (`testId`)

ON DELETE RESTRICT ON UPDATE CASCADE;

);

ALTER TABLE `lab1`.`test` ADD testMarks float not null; -- To add a column

in a table, use the following syntax via Query

-- DESCRIBE `lab1`.`test`;

ALTER TABLE `lab1`.`test1` ADD PRIMARY KEY(`test1Id`); -- To alter and

add a primary key in 2nd table, use the following syntax via Query

-- EXPLAIN `lab1`.`test1`;

ALTER TABLE `lab1`.`test` ADD CONSTRAINT `fk_test` FOREIGN KEY

(`test1Id`) REFERENCES `lab1`.`test1`(`test1Id`) ON DELETE RESTRICT

ON UPDATE RESTRICT; -- By Altering and adding a foreign key constraint in

first table, use the following syntax via Query

-- EXPLAIN `lab1`.`test`;

http://localhost/phpmyadmin/url.php?url=http://dev.mysql.com/doc/refman/5.5/en/delete.html

http://localhost/phpmyadmin/url.php?url=http://dev.mysql.com/doc/refman/5.5/en/update.html

http://localhost/phpmyadmin/url.php?url=http://dev.mysql.com/doc/refman/5.5/en/alter-table.html







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ALTER TABLE `lab1`.`test1` DROP FOREIGN KEY `fk_1`;

ALTER TABLE `lab1`.`test1` ADD CONSTRAINT `fk_test1` FOREIGN

KEY (`testId`) REFERENCES `lab1`.`test`(`testId`) ON DELETE

RESTRICT ON UPDATE RESTRICT;

-- To change the name of the foreign key constraint in a table, firstly drop the

Constraint of Foreign key than again write the whole query as given

/*

Let's look at the ON UPDATE clause:

ON UPDATE RESTRICT: the default: if you try to update a company_id in table

COMPANY the engine will reject the operation if one USER at least links on this

company.

ON UPDATE NO ACTION: same as RESTRICT.

ON UPDATE CASCADE: the best one usually: if you update a company_id in a

row of table COMPANY the engine will update it accordingly on all USER rows

referencing this COMPANY (but no triggers activated on USER table, warning).

The engine will track the changes for you, it's good.

ON UPDATE SET NULL: if you update a company_id in a row of table

COMPANY the engine will set related USERs company_id to NULL (should be

available in USER company_id field). I cannot see any interesting thing to do with

that on an update, but I may be wrong.

And now on the ON DELETE side:








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ON DELETE RESTRICT: the default: if you try to delete a company_id Id in

table COMPANY the engine will reject the operation if one USER at least links on

this company, can save your life.

ON DELETE NO ACTION: same as RESTRICT

ON DELETE CASCADE: dangerous: if you delete a company row in table

COMPANY the engine will delete as well the related USERs. This is dangerous

but can be used to make automatic cleanups on secondary tables (so it can be

something you want, but quite certainly not for a COMPANY<->USER example)

ON DELETE SET NULL: * handful*: if you delete a COMPANY row the

related USERs will automatically have the relationship to NULL. If Null is your

value for users with no company this can be a good behavior, for example maybe

you need to keep the users in your application, as authors of some content, but

removing the company is not a problem for you.

usually my default is:

ON DELETE RESTRICT ON UPDATE CASCADE

with some ON DELETE CASCADE for track tables (logs--not all logs--,

things like that) and ON DELETE SET NULL when the master table is a 'simple

attribute' for the table containing the foreign key, like a JOB table for the USER

table.

*/


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ALTER TABLE `lab1`.`test1` DROP FOREIGN KEY `fk_test1`;


KEY (`testId`) REFERENCES `lab1`.`test` (`testId`) ON DELETE

CASCADE ON UPDATE CASCADE;

/*



KEY (`testId`) REFERENCES `lab1`.`test`(`testId`) ON DELETE

RESTRICT ON UPDATE CASCADE;

*/

ALTER TABLE `LAB1`.`TEST` CHANGE `testName` `test_Name`

VARCHAR (20); -- To change the data type and Name of a column in a table, use

the following syntax `backtick`)

ALTER TABLE `LAB1`.`TEST` CHANGE `test_Name` `testName`

varchar(20); -- To change the data type and Name of a column in a table, use

the following syntax

/* FOEREIGN Keys can have Null Values */














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INSERT INTO `LAB1`.`TEST` (testId, testName, testMarks) VALUES

(1,'Quiz 01',7.5); -- The INSERT INTO statement is used to insert new records in

specific columns in a table

INSERT INTO `LAB1`.`TEST` (testId, testName) VALUES (2, 'Quiz 02'); --

It is also possible to only insert data in specific columns.

INSERT INTO `LAB1`.`TEST1` (test1Id, test1Name) VALUES (1,'Quiz 01'),

(2,'Quiz 02'); -- Inserting Multiple records into a 2nd table VIA Single Query

-- select * from `lab1`.`test1`

UPDATE `lab1`.`test` SET `test1Id` = '1' WHERE `test`.`testId` = 1;

-- Updating and relating Primary and Foreign Key’s in a table via query

UPDATE `lab1`.`test1` SET `testId` = '1' WHERE `test1`.`test1Id` = 1;

-- Updating and relating Primary and Foreign Key’s in second table via query


http://localhost/phpmyadmin/url.php?url=http://dev.mysql.com/doc/refman/5.5/en/set.html


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SELECT * FROM `lab1`.`test` ORDER BY `test`.`testId` ASC; -- To show the

output of all record in Ascending Order

SELECT * FROM `lab1`.`test` ORDER BY `test`.`testId` DESC; -- To show

the output of all record in Descending Order

SELECT testId FROM `lab1`.`test` ORDER BY `test`.`testId` ASC; -- To

show the output of one column in Ascending Order

SELECT testId FROM `lab1`.`test` ORDER BY `test`.`testId` DESC; -- To

show the output of one column in Descending Order

SELECT * FROM `lab1`.`test` WHERE `test`.`testId` < 3

AND

`test`.`testName` = 'Quiz 01'; /*To show the output using

WHERE clause and operator’s */

SELECT * FROM `lab1`.`test` WHERE `test`.`testId` <= 3

AND

`test`.`testName` > 'Quiz 01'; /*To show the output using WHERE clause

and operator’s */




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select * from `lab1`.`test` order by `test`.`testId` limit 2; -- To limit the output

of a record to output of: 1 and 2

select * from `lab1`.`test` order by `test`.`testId` limit 1 offset 1; -- To limit

only output of 2 using offset

select `testId` AS Ìd` FROM `lab1`.`test` ; -- To use the ALIAS to change the

table name temporary

select `testId` AS Ìd` FROM `lab1`.`test` order by Ìd` desc ; -- To use the

ALIAS to change the table name temporary and show output in Descending order

select COUNT(*) from `lab1`.`test`; -- To use the COUNT(*) FUNCTION that

will return the number of records in a table

select COUNT(testMarks) from `lab1`.`test`; -- To use the

COUNT(column_name) FUNCTION that will return the number of records in a

table from a specific selected column


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/*

TRUNCATE TABLE `LAB1`.`TEST`; What if we only want to delete the data

inside the table, and not the table itself. BUT it will generate an error because table

are in primary to foreign relationship

*/

ALTER TABLE `lab1`.`test` DROP FOREIGN KEY `fk_test`;

-- To drop a foreign key in second table, use the following syntax via Query


-- To drop a foreign key in second table, use the following syntax via Query

TRUNCATE TABLE `LAB1`.`TEST`; -- What if we only want to delete the data

inside the table, and not the table itself

TRUNCATE TABLE `LAB1`.`TEST1`; -- What if we only want to delete the

data inside the table, and not the table itself


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ALTER TABLE `LAB1`.`TEST` /* To delete a column in a table having primary

key assigned but no relationship via foreign key, use the following syntax (notice

that some database systems don't allow deleting a column) {this is for Multi

Line Comments} */

DROP COLUMN `testId`;

ALTER TABLE `LAB1`.`TEST` /* To delete a column in a table having primary

key assigned but no relationship via foreign key, use the following syntax (notice

that some database systems don't allow deleting a column) {this is for Multi

Line Comments} */

DROP COLUMN `test1Id`;

ALTER TABLE `LAB1`.`TEST1` /* To delete multiple column in a table

having primary key assigned but no relationship via foreign key, use the following

Efficient syntax */

DROP COLUMN `testId`,

DROP COLUMN `test1Id`;

ALTER TABLE `Lab1`.`TEST` MODIFY COLUMN `testName`

varchar(30); -- To change Only the data type of a column in a table, use the

following syntax


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INSERT INTO `LAB1`.`TEST` VALUES ('Quiz 01',9.5);

INSERT INTO `LAB1`.`TEST` VALUES ('Quiz 02',10);

SELECT * FROM `LAB1`.`TEST` WHERE `testMarks` = '9.5'; -- It is also

possible to select a specific data from a specific colum_name or label_name.

DELETE FROM `LAB1`.`TEST`

WHERE `testMarks`=10; -- It is also possible to delete a data from a specific

ROW.

DROP table if exists `lab1`.`test1`; -- To delete a Table in a Database

CREATE table IF NOT EXISTS `lab1`.`TEST` /* Using Qualifier

Character to quickly select a database and a table via Code using Console.*/

(

testId int(200)

);


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DROP table if exists `lab1`.`test1` , `lab1`.`test`; -- To delete multiple tables in a

Database via One Query

DROP database if exists lab1; -- To delete a Database


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/*

Data Types in MySQL: -

Date and Time Types:

The MySQL date and time datatypes are:

• DATE - A date in YYYY-MM-DD format, between 1000-01-01 and 9999-

12-31. For example, December 30th, 1973 would be stored as 1973-12-30.

• DATETIME - A date and time combination in YYYY-MM-DD

HH:MM:SS format, between 1000-01-01 00:00:00 and 9999-12-31

23:59:59. For example, 3:30 in the afternoon on December 30th, 1973 would

be stored as 1973-12-30 15:30:00.

• TIMESTAMP - A timestamp between midnight, January 1, 1970 and

sometime in 2037. This looks like the previous DATETIME format, only

without the hyphens between numbers; 3:30 in the afternoon on December

30th, 1973 would be stored as 19731230153000 ( YYYYMMDDHHMMSS

).

• TIME - Stores the time in HH:MM:SS format.

• YEAR(M) - Stores a year in 2-digit or 4-digit format. If the length is

specified as 2 (for example YEAR(2)), YEAR can be 1970 to 2069 (70 to

69). If the length is specified as 4, YEAR can be 1901 to 2155. The default

length is 4.

Numeric Data Types:

MySQL uses all the standard ANSI SQL numeric data types, so if you're coming to

MySQL from a different database system, these definitions will look familiar to


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you. The following list shows the common numeric data types and their

descriptions:

• INT - A normal-sized integer that can be signed or unsigned. If signed, the

allowable range is from -2147483648 to 2147483647. If unsigned, the

allowable range is from 0 to 4294967295. You can specify a width of up to

11 digits.

• TINYINT - A very small integer that can be signed or unsigned. If signed,

the allowable range is from -128 to 127. If unsigned, the allowable range is

from 0 to 255. You can specify a width of up to 4 digits.

• SMALLINT - A small integer that can be signed or unsigned. If signed, the

allowable range is from -32768 to 32767. If unsigned, the allowable range is

from 0 to 65535. You can specify a width of up to 5 digits.

• MEDIUMINT - A medium-sized integer that can be signed or unsigned. If

signed, the allowable range is from -8388608 to 8388607. If unsigned, the

allowable range is from 0 to 16777215. You can specify a width of up to 9

digits.

• BIGINT - A large integer that can be signed or unsigned. If signed, the

allowable range is from -9223372036854775808 to 9223372036854775807.

If unsigned, the allowable range is from 0 to 18446744073709551615. You

can specify a width of up to 20 digits.

• FLOAT(M,D) - A floating-point number that cannot be unsigned. You can

define the display length (M) and the number of decimals (D). This is not

required and will default to 10,2, where 2 is the number of decimals and 10

is the total number of digits (including decimals). Decimal precision can go

to 24 places for a FLOAT.

• DOUBLE(M,D) - A double precision floating-point number that cannot be

unsigned. You can define the display length (M) and the number of decimals

(D). This is not required and will default to 16,4, where 4 is the number of


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decimals. Decimal precision can go to 53 places for a DOUBLE. REAL is a

synonym for DOUBLE.

• DECIMAL(M,D) - An unpacked floating-point number that cannot be

unsigned. In unpacked decimals, each decimal corresponds to one byte.

Defining the display length (M) and the number of decimals (D) is required.

NUMERIC is a synonym for DECIMAL.

String Types:

Although numeric and date types are fun, most data you'll store will be in string

format. This list describes the common string datatypes in MySQL.

• CHAR(M) - A fixed-length string between 1 and 255 characters in length

(for example CHAR(5)), right-padded with spaces to the specified length

when stored. Defining a length is not required, but the default is 1.

• VARCHAR(M) - A variable-length string between 1 and 255 characters in

length; for example VARCHAR(25). You must define a length when

creating a VARCHAR field.

• BLOB or TEXT - A field with a maximum length of 65535 characters.

BLOBs are "Binary Large Objects" and are used to store large amounts of

binary data, such as images or other types of files. Fields defined as TEXT

also hold large amounts of data; the difference between the two is that sorts

and comparisons on stored data are case sensitive on BLOBs and are not

case sensitive in TEXT fields. You do not specify a length with BLOB or

TEXT.

• TINYBLOB or TINYTEXT - A BLOB or TEXT column with a maximum

length of 255 characters. You do not specify a length with TINYBLOB or

TINYTEXT.


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• MEDIUMBLOB or MEDIUMTEXT - A BLOB or TEXT column with a

maximum length of 16777215 characters. You do not specify a length with

MEDIUMBLOB or MEDIUMTEXT.

• LONGBLOB or LONGTEXT - A BLOB or TEXT column with a

maximum length of 4294967295 characters. You do not specify a length

with LONGBLOB or LONGTEXT.

• ENUM - An enumeration, which is a fancy term for list. When defining an

ENUM, you are creating a list of items from which the value must be

selected (or it can be NULL). For example, if you wanted your field to

contain "A" or "B" or "C", you would define your ENUM as ENUM ('A',

'B', 'C') and only those values (or NULL) could ever populate that field.

*/

/*

We have three fields as given below, What data type’s we will choose and why?

studentId –

INT

studentFirstName –

VARCHAR


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studentAddress –

VARCHAR

If you look at the list of field types, there is an INT but no Number; and there are

different Text Types to choose from. We can use INT (meaning integer) for the

numbers, but again, there are a few Integer Types to choose from. And that's

leaving out things like float and double. Here's given the difference between them:

Integer Values

TINYINT

Signed: -128 to 127. Unsigned: 0 to 255

SMALLINT


MEDIUMINT


INT



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BIGINT

Signed: -9223372036854775808. Unsigned: 0 to 18446744073709551615

The signed and unsigned are for minus and non-minus values. So, if you need to

store negative values, you need to be aware of the signed ranges. If you were

using a TINYINT value, for example, you can go from minus 128 to positive 127.

If you didn't need the minus value, you can go from 0 to positive 255.

For our address book, we have an ID field. We're using this just to identify a record

(row). Each record will be unique, so it will need a different number for each. We

can set it to one of the INT values. But which one?

If we set ID to TINYINT, then you'd run in to problem if you tried to store more

than 255 records. If you used SMALLINT, you'd have problems if you tried to

store the details of friend number 65536. IF you have more than 65 and half

thousand friends, then you need a different INT type. We'll assume that you don't,

so we'll use SMALLINT

➢ All Integer Types cannot follow the specified range; If range is assigned in

MySQL. So, Choose the One that is accurate as per your requirement against

your preliminary study of field’s

➢ Fields with any of the above Integer type can be made Primary Key.


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Text Types

The length for the text types can be quite confusing. The MySQL manual says this

about the various lengths that each text type can hold:

TINYTEXT L+1 byte, where L < 2^8

TEXT L+2 bytes, where L < 2^16

MEDIUMTEXT L+3 bytes, where L < 2^24

LONGTEXT L+4 bytes, where L < 2^32

This in not terribly helpful for beginners! So, what does it mean. Well, the L + 1

part means, "The length of the string, plus 1 byte to store the value." The translated

values for each are approximately:

TINYTEXT 256 bytes

TEXT 64 KiloBytes

MEDIUMTEXT 16 MegaBytes

LONGTEXT 4 GigaBytes

➢ Text cannot follow the specified range; If range is assigned in MySQL.

➢ Fields with Text data type cannot be made Primary Key’s.

To confuse the issue even more, you can also use CHAR and VARCHAR to store

your text. These are quite useful, if you know how many characters you want to

store. For example, for a UK postcode you don't need more than 9 characters, and

one of those will be a blank space. So, there's no sense in setting a postcode field to

hold 4 gigabytes! Instead, use CHAR or VARCHAR.


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CHAR

You specify how many characters you want the field to hold. The maximum value

is 255.

For example:

CHAR (10)

This field can then hold a maximum of ten characters. But if you only use 4 of

them, the rest of the 10 characters will be blank spaces. The blank spaces get added

to the right of your text:

"TEXT "

"TENLETTERS"

➢ But, if range not specified than it will show only one CHARACTER in the

output.

➢ Fields with CHAR data types can be set as Primary Keys with or without

specifying range.


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VARCHAR

Like CHAR, but the rest of the characters are not padded with blank spaces. The

maximum value before MySQL 5.0.3 was 255. After this it's jumped to 65, 535.

With VARCHAR, there is also an extra byte that records how long your text is.

➢ But, if range not specified than MySQL creates a logical error.

➢ Fields with VARCHAR data types can be set Primary Keys but range must

be assigned.

UNIQUE

The UNIQUE constraint in MySQL does not allow to insert a duplicate value in a

column. The UNIQUE constraint maintains the uniqueness of a column in a table.

More than one UNIQUE column can be used in a table.

Null Constraint

This is an important field in database terminology. It essentially means, "Should

the field contain anything?" If you set a field to NOT NULL, then you can't leave it

blank when you come to adding records to your database. Otherwise you'll get

errors.


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Extra (earlier versions of phpMyAdmin)

This is where you can set an auto increment value. This means adding one to the

previous record number. This is ideal for us, as we have an ID field. Then we don't

have to worry about this field. MySQL will take care of updating it for us.

*/


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-- Implementation of Data Types via Code using Console: -

drop database if exists `lab`;

create database if not exists `lab`;

/*

drop table if exists `lab`.`std`;

create table if not exists `lab`.`std`

(

stdName varchar not null primary key

);

insert into `lab`.`std` values ('Nouman Farooq'), ('Arslan Farooq');


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select * from `lab`.`std`;

*/

/*

drop table if exists `lab`.`std1`;

create table if not exists `lab`.`std1`

(

stdName varchar (7) not null primary key

);

insert into `lab`.`std1` values ('Nouman Farooq'), ('Arslan Farooq');

select * from `lab`.`std1`;

*/


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/*



(

stdName char not null primary key

);



*/


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/*



(

stdName char (7) not null primary key

);



*/


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/*



(

stdName text not null primary key

);



*/

/*



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(

stdName text(6) not null primary key

);



*/

/*



(


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stdName char not null primary key

);


UPDATE `lab`.`std6` SET stdName = 'Muhammad Farooq Khan'

where stdName = 'Arslan Farooq';


*/


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-- Joining Concepts - DS_ISP_Lecture 8 (Coding)

drop database if exists `JOINING`;

create database if not exists `JOINING`;

USE `JOINING`;

CREATE TABLE `JOINING`.`DEPARTMENT`

(

DepartmentId varchar(4) not null PRIMARY KEY,

DepartmentName text (12) not null

);

CREATE table `JOINING`.`EMPLOYEE`

(

LastName text (12),

DepartmentId varchar (4)

);


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INSERT INTO `Joining`.`DEPARTMENT` VALUES (31,'Sales') ,

(33,'Engineering') , (34,'Clerical') , (35,'Marketing') ;

INSERT INTO `Joining`.ÈMPLOYEE` (`LastName`, `DepartmentId`)

VALUES ('Rafferty', 31) , ('Jones', 33) , ('Heisenberg', 33) , ('Robinson', 34),

('Smith', 34) , ('Williams', ''); -- for insertion of empty value we use: ''

-- Cros Join: -

SELECT * from `JOINING`.ÈMPLOYEE`

CROS JOIN

`JOINING`.`Department`

ORDER BY `CROS`.`DepartmentId` ASC; -- Example of an Explicit

Cross Join

SELECT * from `JOINING`.ÈMPLOYEE` , `JOINING`.`Department`

ORDER BY ÈMPLOYEE`. `LastName` ASC; -- Example of an Implicit

Cross Join

/* Something is implicit when it is implied but not directly stated. Something is

explicit when it is directly stated and leaves no room for uncertainty. */



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-- Inner Join: -

/*

1. An inner join requires each record in the two joined tables to

have matching records.

2. Inner join creates a new result table by combining column values

of two tables (A and B) based upon the join-condition.

3. The query compares each row of A with each row of B to find all

pairs of rows which satisfy the join-condition.

*/

/* The "explicit join notation" uses the JOIN keyword, optionally

preceded by the INNER keyword, to specify the table to join, and the

ON keyword to specify the condition for the join, as in the following

example:

*/


Inner JOIN `JOINING`.`Department`

ON `Employee`.`DepartmentId` = `department`.`DepartmentId`

ORDER BY `EMPLOYEE`.`DepartmentId` ASC;


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-- The following example is equivalent to the previous one, but this time using

implicit join notation:

SELECT * from `JOINING`.ÈMPLOYEE` , `JOINING`.`Department`

WHERE

ÈMPLOYEE`.`DEPARTMENTId` = `DEPARTMENT`.`DEPARTMENTId`

ORDER BY ÈMPLOYEE`.`DepartmentId` ASC;

-- Outer Join: -

/*

1. An Outer Join does not require each record in the two joined

tables to have a matching record.

2. The joined table retains each record; even if no other matching

record exists.

3. Outer joins subdivide further into left outer joins, right outer joins,

and full outer joins, depending on which table's rows are retained


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(left, right, or both). (In this case left and right refer to the two

sides of the JOIN keyword.)

4. No implicit join-notation for outer joins exists in standard SQL.

*/

-- Left Outer Join: -

/*

1. The result of a left outer join (or simply left join) for tables A and B always

contains all records of the "left" table (A), even if the join condition does not

find any matching record in the "right" table (B).

2. This means that if the ON clause matches 0 (zero) records in B (for a given

record in A), the join will still return a row in the result (for that record) but

with NULL in each column from B.

3. A left outer join returns all the values from an inner join plus all values in

the left table that do not match to the right table, including rows with NULL

(empty) values in the link field.

For example, this allows us to find an employee's department, but still shows the

employee(s) even when they have not been assigned to a department (contrary to


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the inner-join example above, where unassigned employees were excluded from

the result).

Example of a left outer join (the OUTER keyword is optional), with the additional

result row (compared with the inner join):

-- SYNTAX to Use LEFT JOIN Condition: -

-- SELECT < selected list of fields for all fields use *> FROM

left_table LEFT JOIN right_table ON left_table.right_id =

right_table.id;

-- AND

-- SELECT < selected list of fields for all fields use *> FROM

left_table LEFT JOIN right_table ON right_table.left_id =

left_table.id;

*/

/*


LEFT JOIN


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`JOINING`.`DEPARTMENT`

ON

ÈMPLOYEE`.`DEPARTMENTId` = `DEPARTMENT`.`DEPARTMENTId`

ORDER BY ` DEPARTMENT`.`DepartmentName` ASC;

*/

-- SELECT * from `JOINING`.ÈMPLOYEE` LEFT OUTER JOIN

`DEPARTMENT` ON ÈMPLOYEE`.`DEPARTMENTId` =

`DEPARTMENT`.`DEPARTMENTId` ORDER BY

ÈMPLOYEE`.`DepartmentId` ASC;

-- SELECT LASTNAME, DEPARTMENTNAME from

`JOINING`.`department` left JOIN èmployee` ON

`DEPARTMENT`.`DEPARTMENTId` =

ÈMPLOYEE`.`DEPARTMENTId`;


`JOINING`.`department` LEFT JOIN èmployee` ON

`department`.`DEPARTMENTId` = èmployee`.`DEPARTMENTId`

WHERE `DEPARTMENT`.`DEPARTMENTNAME` = 'SALES' ORDER BY

ÈMPLOYEE`.`LASTNAME` ASC;


`JOINING`.`department` LEFT JOIN èmployee` ON


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`department`.`DEPARTMENTId` = èmployee`.`DEPARTMENTId`

WHERE ÈMPLOYEE`.`LASTNAME` = 'RAFFERTY';

-- SELECT ÈMPLOYEE`.`DEPARTMENTID`, LASTNAME,

DEPARTMENTNAME from `JOINING`.`department` LEFT JOIN

èmployee` ON `department`.`DEPARTMENTId` =

èmployee`.`DEPARTMENTId` WHERE

ÈMPLOYEE`.`DEPARTMENTID` = '31';

-- SELECT ÈMPLOYEE`.`DEPARTMENTID`, LASTNAME,




ÈMPLOYEE`.`DEPARTMENTID` = 31;

-- SELECT EMPLOYEE.DEPARTMENTID, LASTNAME,




ÈMPLOYEE`.`DEPARTMENTID` > 31 AND

ÈMPLOYEE`.`DEPARTMENTID` < 34;


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-- Right Outer Join: -

/*

1. A right outer join (or right join) closely resembles a left outer join, except

with the treatment of the tables.

2. Every row from the "right" table (B) will appear in the joined table at least

once. If no matching row from the "left" table (A) exists, NULL will appear

in columns from A for those records that have no match in B.

3. A right outer join returns all the values from the right table and matched

values from the left table (NULL in the case of no matching join predicate).

For example, this allows us to find each employee and his or her department,

but still show departments that have no employees.

-- SYNTAX to Use RIGHT JOIN Condition: -

-- SELECT <select list> FROM left_table RIGHT JOIN right_table ON

left_table.id = right_table.id;

-- AND

-- SELECT <select list> FROM left_table RIGHT JOIN right_table ON

right_table.id = left_table.id;

*/


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-- Below are some examples of a right outer join (the OUTER keyword is

optional):

-- SELECT * from `JOINING`.ÈMPLOYEE` RIGHT OUTER JOIN

`DEPARTMENT` ON ÈMPLOYEE`.`DEPARTMENTId` =

`DEPARTMENT`.`DEPARTMENTId` ORDER BY

ÈMPLOYEE`.`DepartmentId` ASC;


`JOINING`.`department` right JOIN èmployee` ON

`DEPARTMENT`.`DEPARTMENTId` =

ÈMPLOYEE`.`DEPARTMENTId`;



`department`.`DEPARTMENTId` = èmployee`.`DEPARTMENTId`;



`department`.`DEPARTMENTId` = èmployee`.`DEPARTMENTId` ORDER

BY ÈMPLOYEE`.`LASTNAME` DESC;


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-- Full Join: -

/*

1. Conceptually, a full join combines the effect of applying both left and right

outer joins.

2. Also, records in the FULL JOIN tables do not match; the result set will have

NULL values for every column of the table that lacks a matching row. For

those records that do match, a single row will be produced in the result set

(containing fields populated from both tables).

For example, this allows us to see each employee who is in a department and

each department that has an employee, but also see each employee who is not

part of a department and each department which doesn't have an employee.

Important Note:

We don't have FULL JOINS on MySQL, but we can sure use this query to get our desired result as per full join definition.

Syntax with Two Tables “t1 and t2”: -

SELECT * FROM `db_name`.`t1`

LEFT JOIN `t2` ON `t1`.`column_name` = `t2`.`column_name`

UNION ALL

SELECT * FROM `db_name`.`t1`

RIGHT JOIN `t2` ON `t1`.`column_name` = `t2`.`column_name`

*/


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-- Below is an example of a full outer join (the OUTER keyword is optional):


LEFT JOIN `JOINING`.`DEPARTMENT`

ON ÈMPLOYEE`.`DEPARTMENTId` =

`DEPARTMENT`.`DEPARTMENTId`

UNION ALL

SELECT * FROM `JOINING`.ÈMPLOYEE`

RIGHT JOIN

`JOINING`.ÈMPLOYEE`

ON ÈMPLOYEE`.`DEPARTMENTId` = `DEPARTMENT`.`departmentId`;

-- End of Lab Activities Detailed Review- MySQL Coding Using Console

department of computer science & it...jan 01, 1970 · a student may borrow some books from the...

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