SQL (Standard Query Language)

Yong Choi

School of Business

CSU, Bakersfield

2

Study Objectives

• Understand the basic commands and functions of SQL

• Learn how to use SQL to query a database to extract useful information

• Practice SQL

3

Introduction to SQL

• Standard Query Language (SQL) is a computer language for the relational database model.

• SQL is a nonprocedural language (click here for the example). So, it is much easier to use. – what is to be done without having to worry about how

it's to be done.• Procedural language (click here for the example)

– Must be programmed correctly and compiled– Java, C++, and Pascal.

• SQL is relatively easy to learn– SQL commands set has a basic vocabulary of less than

100 words.

Go To Next Topic

4

SQL Example

SELECT ID, L_Name, F_Name, Salary, Dept_No

FROM Employee; 

ID L_Name F_Name Salary Dept_No

--------- ---------- ---------- ---------- -------------------------------------------------------------------------

1 Kim John 1000 100

2 Johnson Steve 1200 100

3 Jonson Paul 1100 200

4 Lee Jim 1100 200

5 Basinger Jon 1300

6 Stone Sharon 1000

 6 rows selected.

Back

5

JAVA Example

public class JavaProgramming{

public static void main ( String[] args ) { long payAmount; payAmount = 123; System.out.println("The variable contains: " + payAmount ); }

}

• Output: The Variable contains 123.

Back

6

Basic SQL Commands

• Followings are the most frequently used commands – Use always

• SELECT <field list>• FROM <table list>

– Use when conditions must be specified • WHERE <condition>• HAVING <group condition>

• ORDER BY <sorting field>• GROUP BY < grouping records>

7

The SELECT and FROM Statement

• Need both commands almost always…..– The SELECT statement is used to select data from

a table. – The FROM statement is used to select tables.

• Syntax:– SELECT column_name(s) – FROM table_name

• To select all columns (fields) from a table, use * symbol instead of column names: – SELECT * – FROM table_name

8

The WHERE Statement

• To conditionally select data from a table, a WHERE clause can be added to the SELECT statement.

• Syntax:– SELECT column

– FROM table

– WHERE column operator value • See next slide for various operators

9

SQL Comparison Operators FOR WHERE clause

AND logical operator

OR logical operator

NOT Warehouse =‘3’

LIKE: LIKE ‘a*’, LIKE ‘*s’, Like ‘*Oxford*’

BETWEEN 45000 AND 78000

10

Semicolon after SQL Statements?

• Semicolon is the standard way to a block of SQL statement in database systems. So, you must use a semicolon at the end of a block of SQL statement.– Access SQL commands are not case sensitive but

try to follow exact names for better readability.

• Download SQL data file form the class web site.– SQL_300.mdb

11

CustomerNum CustomerName Street City State Zip Balance CreditLimit RepNum

148 Al's Appliance and Sport

2837 Greenway

Fillmore FL 33336 $6,550 $7,500 20

OrderNum PartNum NumOrdered QuotedPrice

21608 AT94 11 $21.95

OrderNum OrderDate CustomerNum

21608 10/20/2003 148

Customer

OrderLine

Orders

PartNum Description OnHand Class Warehouse Price

AT94 Iron 50 HW 3 $24.95

Part

Rep

RepNum LastName FirstName Street City State Zip Commission Rate

20 Kaiser Valerie 624 Randall Grove FL 33321 $20,542.50 0.05

12

SQL Preparation

• Review tables and relationships first…– Review each table in both views

• Design view• Datasheet view

– Recognize PK and FK information

– Examine Relationships information

• SQL using Access– Design view of query Select SQL View using

Style button

– No need to add tables (unlike QBE)

13

SQL Sample

• I’d like to know the list of CustomerNum and CustomerName.– SELECT CustomerNum, CustomerName– FROM Customer;

• I’d like to know the list of PartNum, Description, RepNum, and LastName– SELECT PartNum, Description, RepNum, LastName– FROM Part, Rep;

14

SQL Example 1 & 2

• Example 1: – I’d like to know a list of the Customer number,

Customer name, and balance of all customers.– Save as SQL 1

• Example 2:– I’d like to know a list of the Order number, Part

number, Price and Order Date.– Save as SQL 2

15

SQL Example 3

• Restriction requirements– Where command– Exact Match

• Example 3: – I’d like to know customer names who are located

in the city of Grove– Save as SQL 3

16

SQL Query to Find All Customers in ‘Grove’

17

SQL Example 4

• Restriction requirements– Where command– Comparison operator

• Example 4:– I’d like to know a list of the number, name, credit

limit, and balance for customers with credit limits that exceed their balances.

– Save as SQL 4

18

Query to find Customers with Credit Limit Exceeding Balance

19

SQL Example 5

• Restriction requirements– Where command– Compound conditions

• Example 5: – List the description of all parts that are located in

warehouse 3 and for which there are more than 20 units on hand.

– Save as SQL 5

20

SQL Query with Compound Condition using ‘AND’

21

SQL Example 6

• Default value of ORDER BY: ascending

• Example 6:– List the number, name, and credit limit of all

customers. Sort the customers by name in ascending order.

– Save as SQL 6

22

SQL Query to Sort Data