1 the oracle database system building a database database course the hebrew university of jerusalem
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1
The Oracle Database System
Building a Database
Database CourseThe Hebrew University of Jerusalem
2
Technical Basics
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Connecting to the Database
At the command line prompt, write:
sqlplus login/[email protected]
In the beginning your password is the same as your login. You can change your password with the command:
password
To disconnect use the command:quit
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Connecting to the Database
5
Running SQL Files
Instead of typing SQL commands into the SQLPLUS terminal, you can load commands from a file Use the command @file from SQLPLUS to load
the file file.sql Invoke the SQLPLUS command with the extra
parameter @file to load the file at connection: sqlplus login/[email protected] @file
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Spooling the Output
Output can be placed in a file: spool myFile.out
Spooling can be turned off with: spool off
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Tables Creation
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Creating a Table
The basic format of the CREATE TABLE command is:
CREATE TABLE TableName(Column1 DataType1 ColConstraint, …ColumnN DataTypeN ColConstraint,TableConstraint1, …TableConstraintM
);
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An Example
If you issue the command describe Cars you get:
Name Null? Type
-------- ----- ------------
LICENSE NUMBER
COLOR VARCHAR2(15)
CREATE TABLE Cars(License NUMBER,Color VARCHAR2(15));
Note that the definition is case insensitive
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Data Types
CHAR(n) String of length n (n <= 2000)
VARCHAR2(n) Variable length string of size <= n
(n <= 4000)
DATE Valid dates
CLOB Character large object (<= 4Gb)
NUMBER Up to 40 digits
NUMBER(n) Number of size n
NUMBER(n,m) Number of size n with m digits after decimal place
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Constraints in Create Table
Adding constraints to a table enables the database system to enforce data integrity.
However, adding constraints also makes inserting data slower.
• Different types of constraints:* Not Null * Default Values* Unique * Primary Key* Foreign Key * Check Condition
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Not Null Constraint
CREATE TABLE Employee(SSN NUMBER NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1),Salary NUMBER(5) NOT NULL,Dept NUMBER
);
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Default Values
CREATE TABLE Employee(SSN NUMBER NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER
);
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CREATE TABLE Employee(SSN NUMBER UNIQUE NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER,constraint Emp_UQ UNIQUE(Fname, Lname)
);
Unique Constraint
The name of the constraint
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Primary Key Constraint
CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER,constraint Emp_UQ UNIQUE(Fname, Lname)
);
Primary Key implies NOT NULL and UNIQUE. There can only be one primary key.
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Another Table
CREATE TABLE Department(DeptNum NUMBER PRIMARY KEY,Name VARCHAR2(20),ManagerId NUMBER
);
Shouldn’t all department numbers in Employee appear in Department?
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Foreign Key Constraint(Referential Integrity)
CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER, constraint Emp_UQ UNIQUE(Fname, Lname),FOREIGN KEY (Dept) REFERENCES
Department(DeptNum));
Must be unique
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Alternative Notation
CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER REFERENCES Department(DeptNum),constraint Emp_UQ UNIQUE(Fname, Lname)
);
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Understanding Foreign Keys
The constraint on the last table should be read as: “The field Dept in Employee is a foreign key that references the field DeptNum in Department”
Meaning: Every non-null value in the field Dept in Employee must appear in the field DeptNum in Department.
What happens to Employees in department 312 when Department 312 is removed from the Department table?
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Deleting a Referenced Value If nothing additional is specified, then Oracle will not allow Department 312 to be
deleted if there are Employees working in this department. If the constraint is written as
FOREIGN KEY (Dept) REFERENCES
Department(DeptNum) ON DELETE CASCADE
then Employees working in 312 will be deleted
automatically from the Employee table
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Cyclic Foreign Keys
CREATE TABLE Department(
DeptNum NUMBER PRIMARY KEY,
Name VARCHAR2(20),
ManagerId NUMBER REFERENCES Employee(SSN)
);
Do you see a problem in inserting data now?
We should revise the Department table:
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Solution to Cyclic Constraints
Add one of the constraints later on (after insertion):
ALTER TABLE Department
ADD(FOREIGN KEY (ManagerId)
REFERENCES Employee(SSN));
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Check Conditions
A check condition is a Boolean expression: “And”s and “Or”s of conditions of the type X > 5…
On a column: it can refer only to the column
On a table: it can refer only to multiple columns in the table
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Check Constraints
CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’)
CHECK(Gender = ‘F’ or Gender = ‘M’) ,
Salary NUMBER(5) NOT NULL,CHECK (Gender = ‘M’ or Salary > 10000)
);
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Table Alteration
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Altering Tables
Table definition can be altered after its creation Adding columns Changing columns’ definition Dropping columns Adding constraints And more…
Use the reserved word ALTER
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Altering Tables (continues)
Adding a column:ALTER TABLE Employee ADD (
Mname VARCHAR2(20),Birthday DATE
); Changing columns’ definition:
ALTER TABLE Emplyee Modify (Mname VARCHAR2(10)
);
Cannot be NOT NULL unless the
table is empty
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Altering Tables (continues)
Dropping columns:ALTER TABLE Employee DROP COLUMN
Mname;
Dropping multiple columns:
ALTER TABLE Employee DROP (Mname, Birthday);
Adding constraints:ALTER TABLE Department ADD(
FOREIGN KEY (ManagerId) REFERENCES Employee(SSN));
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Deleting a Table
To delete the table Employee :
DROP TABLE Employee;
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User’s Table List
ORACLE may print tables that hold some general information about the tables in your database
Such Tables are: Tab, Cat, User_Tables (too detailed...)
To see the list of all your tables you can print: SELECT * FROM Cat; SELECT tname FROM Tab; SELECT table_name from User_Tables;
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Table Data Maintenance
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The Employee Table
> Describe Employee
Name Null? Type-------- -------- ------------SSN NUMBERFNAME VARCHAR2(20)LNAME VARCHAR2(20)GENDER CHAR(1)SALARY NOT NULL NUMBER(5)
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Inserting a Row
To insert a row into the Employee table:INSERT INTO
Employee(SSN, Fname, Lname, Salary)
VALUES(121, ‘Sara’, ‘Cohen’,10000);
The remaining columns get default values (or NULL)
Order is not important
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Some More Details…
The fields needn’t be specified if values are specified for all columns and in the order defined by the table
Example:INSERT INTO Employee
VALUES(121, ‘Sara’, ‘Cohen’, `F’, 10000);
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Deleting Rows
General format:DELETE FROM Table WHERE Cond;
Deletes all rows satisfying Cond from Table For example, to remove the employee with
SSN 121 from the Employee table:DELETE FROM Employee WHERE
SSN = 121;
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Deleting Rows (continues)
To remove all male employees having a salary greater than 15000 shekels:
DELETE FROM Employee WHERE
Gender = ‘M’ AND Salary > 15000;
We will later discuss WHERE clauses…
Case sensitive
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Updating Rows (continues)
We can update fields of rows in a table General format:
UPDATE Table SET Field1=value1,,,FieldN=valueNWHERE Cond
Now we can reduce salaries instead of firing employees:
UPDATE Employee SET Salary = 15000 WHERE Gender = ‘M’ AND
Salary > 15000;
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The ORACLE Bulk Loader
A tool that provides easy insertion of large amounts of rows into tables.
The idea: the field values of the rows are kept in a file, the format of which is defined by us.
For example, it can automatically load 3 employees from the file myEmployees.dat that contains the following lines:
Sara|Cohen|121Benny|Kimelfeld|134Yaron|Kanza|156
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The Control File
The control file is the direct input of the loader A simple control file:
LOAD DATA
INFILE <dataFile> [APPEND] INTO TABLE <tableName> FIELDS TERMINATED BY '<separator>‘(<list of all attribute names to load>)
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The Control File (continues)
<dataFile>: The name of the data file
<tableName>: The name of the table into which the data will be loaded
(appended if APPEND is specified, or else the table must be empty)
<separator>: A string that separates two field values of a row
The attributes are separated by commas and enclosed in parentheses
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The Control File (continues)
As an example, the following control file loads the employees from myEmployees.dat:
LOAD DATA
INFILE myEmployees.dat INTO TABLE Employees FIELDS TERMINATED BY '|' (Fname, Lname, SSN)
The attributes that are unspecified will be set to NULL
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The Data File
The Bulk Loader considers every single line to represent one row in the table Even an empty line! (which will usually result in
an error) Spaces are not ignored in the data file!
thus the rows ‘sara| cohen|121’ and ‘sara|cohen|121’ define different functionalities
The NULL value is implied by the NULL keyword or the empty string
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The Data File (continues)
The control and the data files can be combined into one .ctl file using the following format:
LOAD DATA INFILE *INTO TABLE Employees FIELDS TERMINATED BY '|' (Fname, Lname, SSN)BEGINDATA Sara|Cohen|121Benny|Kimelfeld|134Yaron|Kanza|156
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The Bulk Invocation
To invoke the bulk loader, issue the following command directly from the Unix shell:sqlldr <yourName> control=<ctlFile> log=<logFile> bad=<badFile>
All fields are optional File names that have no extension are
automatically extended (by .dat, .log or .bad) Erroneous lines in the data file are ignored
and written into badFile, and any other relevant information is written into logFile.
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Bulk Loader Important Remarks
Before using the Bulk Loader, make sure your personal ORACLE environment is properly set up
The tables you fill using the Bulk Loader should be created prior to the loader invocation
Before invoking the Bulk Loader you have to make sure that NO SQLPLUS SESSIONS ARE OPENNED!
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Table Printing and Formatting
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Format Example
Consider the following table print:
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Format Example (continues)
Absolutely not readable! Solution: we write some commands in a format file
and we get:
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Printing a Table
To print a table use the sql command: SELECT * FROM table_name;
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Add a Title
We can add a title to a table printing page using the command: TTITLE ‘title’
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Change a Column’s Heading
We can change a column’s heading using the command: COLUMN ‘col_name’ HEADING ‘heading’
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Define a Column Size
We can define the size of a column: COLUMN ‘col_name’ format ‘format’ Format Examples:
a18: an ASCII text of size 18 90.99: a number with 4 digits, a decimal point,
minus sign (for negative numbers) and 0 before the dot for numbers smaller than 1
We can ask ORACLE to cut words to fit the defined space using the command: COLUMN ‘col_name’ truncated
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Define a Column Size
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The Whole Picture