Chapter 3: SQL – Part I

Yong Choi

School of Business

CSU, Bakersfield

2

Study Objectives

• Understand the basic commands and functions of SQL

• Learn how SQL is used for data manipulation (to add, modify, delete, and retrieve data)

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

• Learn how SQL is used for data administration (to create tables, indexes, and views)

• Practice SQL

3

Ideal Database Language Requirements

• Create database and table structures. – SQL has a data definition component that gives us

the ability to meet this requirement.

• Manage the data component of the database.– SQL gives us a set of commands to add, update,

and delete data within the database tables.

• Provide detailed data query capability.– "Standard" SQL uses a set of approximately thirty

commands that allow us to retrieve data and to convert the raw data into useful information.

4

Introduction to SQL

• Standard Query Language (SQL) is the relational model’s standard language.

• The original version of SQL was developed at IBM's San Jose Research Laboratory. This language, originally called Sequel. The Sequel language has evolved since then, and its name has changed to SQL (Structured Query Language).

• In 1986, the American National Standards Institute (ANSI) published an SQL standard.– In 1992, work was completed on a significantly

revised version of the SQL standard (SQL-92).

5

Introduction to SQL (con’t)

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

than 100 words.

• SQL is a nonprocedural language. So, it is much easier to use. – Its user merely commands what is to be done

without having to worry about how it's to be done.

– Procedural language: COBOL, C, or Pascal.

6

More about SQL

• Three basic data functions by SQL, and their basic SQL commands:

1. Data definition through the use of CREATE2. Data manipulation through INSERT, UPDATE, and

DELETE3. Data querying through the use of SELECT AND

MANY OTHERS, which is the basis for all SQL queries.

– We will try this first since we just completed all Access queries.

7

Basic Structure of SQL Queries

• SQL relation is not a set of tuples because a set does not allow two identical members; rather it is a multi-set (a bag) of tuples.

 • A SQL query has the form:

 

SELECT <attribute list>

FROM <table list>

[WHERE <condition>]

[GROUP BY < grouping attribute(s)>]

[HAVING <group condition>]

[ORDER BY <attribute list>]

8

The SELECT and FROM Statement

• The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result set). The FROM statement is used to select tables.

• Syntax:– SELECT column_name(s)

– FROM table_name

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

9

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

10

Typical Data Types

• INTEGER– Numbers without a decimal point

• SMALLINT– Uses less space than INTEGER

• DECIMAL(p,q)– P number of digits; q number of decimal places

• CHAR(n)– Character string n places long

• DATE– Dates in DD-MON-YYYY or MM/DD/YYYY

11

Semicolon after SQL Statements?

• Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.

• MS Access and SQL Server 2000 do not require to put a semicolon after each SQL statement, but other database SQLs force you to use it such as Oracle. So, you must use a semicolon for this class.– Access SQL commands are not case sensitive

(including table and attribute names) but try to follow exact names for better readability.

– Download SQL data file form the class web site.

12

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

13

SQL Examples

• Example 2: Save as example 2– List the number, name, and balance of all

customers.

• Example 3: Save as example 3– List the complete Part table.

14

Oracle 7.0 SQL Example

SQL> select * from employee;

 

EMP_ID EMP_LNAME EMP_FNAME EMP_SALARY EMP_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.

15

SQL Examples – WHERE clause

• Example 4: Save as example 4– List the name of every customers with $10,000

credit limit.

• Example 5: Save as example 5– Find the name of customer 148.

16

SQL Comparison Operators FOR WHERE clause

AND / OR logical operators

NOT Warehouse =‘3’

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

(NOT) BETWEEN 45000 AND 78000

(NOT) IN (123, 345)

17

SQL Examples

• Example 6: Save as example 6– Find the customer name for every customer

located in the city of Grove

• Example 7: Save as example 7– List the number, name, credit limit, and

balance for customers with credit limits that exceed their balances.

18

SQL Examples – Compound Conditions

• Example 8: Save as example 8– List the description of all parts that are located

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

• Example 9: Save as example 9– List the descriptions of all parts that are

located in warehouse 3 or for which there are more than 20 units on hand.

19

SQL Examples

• Example 10: Save as example 10– List the description of all parts that are not in

warehouse 3.

• Example 11: Save as example 11– List the number, name, and balance of all

customers with balances greater that or equal to $1,000 and less than or equal to $5,000.

20

SQL Examples – Computed Field

• Computed field can involve:– addition(+), subtraction(-), Multiplication(*), or division (/)

• Example 12: Save as example 12– List the number, name and available credit for

all customers. • Example 13: Save as example 13

– List the number, name, and available credit for all customers with credit limits that exceed their balances.

21

SQL Examples – LIKE and IN

• Example 14: Save as example 14– List the number, name, and complete address of every

customer located on a street that contain the letters “Oxford.” – like *oxford*

• Customer name start with “A” – like a*

• Customer address end with letter “d” – like *d

• Example 15: Save as example 15– List the number, name, and credit limit for every

customer with a credit of $7,500, $10,000, or $15,000.• Use “in” operator

22

SQL Examples

• Default value of ORDER BY: ascending• Example 16: Save as example 16

– List the number, name, and credit limit of all customers. Sort the customers by name in ascending order .

• Example 17: Save as example 17– List the number, name, and credit limit of all

customers. Sort the customers by name in ascending order within credit limit in descending order.