Introduction to SQL

Yong ChoiSchool of BusinessCSU, Bakersfield

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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

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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.

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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).

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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.

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Basic Structure of SQL Queries

• SELECT <attribute list>• FROM <table list>• WHERE <condition>• GROUP BY < grouping attribute(s)>• HAVING <group condition>• ORDER BY <attribute list>

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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

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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

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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

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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 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.

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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

Order

PartNum Description OnHand Class Warehouse Price

AT94 Iron 50 HW 3 $24.95

Part

RepRepNum LastName FirstName Street City State Zip Commission Rate

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

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Example 1

• Example 1: Save as example 1– List the number, name, and balance

of all customers.

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Example 1

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Example 1

SELECT Customernum, CustomerName, Balance

FROM Customer;

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Example 2

• Example 2: Save as example 2– List the complete Part table.– Use of “ * “

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Example 2

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Example 2

SELECT *FROM Part;

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SQL Example – WHERE clause

• Example 3: Save as example 3– List the name of every customers with

$10,000 credit limit.• Credit limit must be equal to $10000

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Example 3SQL Query with Where Condition

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Example 3

SELECT CustomernameFROM CustomerWHERE

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SQL Example – WHERE clause

• Example 4: Save as example 4– Find the name of customer 148.

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Example 4SQL Query to Find Customer 148

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Example 4

SELECT CustomerNumFROM CustomerWHERE

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SQL Comparison Operators For WHERE clause

NOT Warehouse =‘3’

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

(NOT) BETWEEN 45000 AND 78000

(NOT) IN (123, 345)

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SQL Examples

• Example 5: Save as example 5– Find the customer name for every

customer located in the city of Grove

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Example 5

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Example 5

SELECT CustomernameFROM CustomerWHERE

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SQL Examples

• Example 6: Save as example 6– List the number, name, credit limit,

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

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Example 6

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Example 6

SELECT CustomerName, CustomerName, CreditLimit, Balance

FROM CustomerWHERE

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SQL Examples – Compound Conditions

• Example 7: Save as example 7– List the description of all parts that

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

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Example 7SQL Query with Compound Condition

using ‘AND’

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Example 7

SELECT DescriptionFROM PartWHERE

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SQL Examples – Compound Conditions

• Example 8: Save as example 8– List the descriptions of all parts that

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

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Example 8SQL Query using ‘OR’

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Example 8

SELECT DescriptionFROM PartWHERE

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SQL Examples

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

are not in warehouse 3. – Use “NOT” (i.e., where NOT A = 100;)

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Example 9SQL Query using ‘NOT’

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Example 9

SELECT DescriptionFROM PartWHERE NOT

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SQL Examples

• Example 10: Save as example 10– List the number, name, and balance

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

– (NOT) BETWEEN 45000 AND 78000

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Example 10Query with ‘BETWEEN’ Operator

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Example 10

SELECT CustomerNum, CustomerName, Balance

FROM CustomerWHERE

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SQL Examples – Computed Field

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

division (/)

• Example 11: Save as example 11– List the number, name and available

credit for all customers. – Use “AS” for assigning a new field

name

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Example 11SQL Query with Computed Field

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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 with credit limits that exceed their balances.

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Example 12SQL Query with Computed

Field and Condition

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SQL Examples – LIKE and IN

• Example 13: Save as example 13– List the number, name, and complete

address of every customer located on a street that contain the letters “Oxford.” • Customer names begin with B: Like B*• Customer names end with E: Like *E• Fine exact customer last name: like

‘*Choi*’

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Example 13SQL Query with ‘LIKE’ Operator

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SQL Examples – LIKE and IN

• Example 14: Save as example 14– List the number, name, and credit

limit for every customer with a credit of $7,500, $10,000, or $15,000.

– IN (7500, 10000, 15000);

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Example 14SQL Query with ‘IN’ Operator

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SQL Examples

• Default value of ORDER BY: ascending• Example 15: Save as example 15

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

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Example 15SQL Query to Sort Data

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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 (minor) in ascending order within credit limit (major) in descending order.

– What about this case? • customer name (minor) and credit limit (major)

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Example 16SQL Query to Sort on Multiple Fields