1. Chapter # 7
Introduction to
Structured Query Language (SQL)
Part I

2. Introduction to SQL SQL functions fit into two broad categories:
Data definition language
Data manipulation language
Basic command set has vocabulary of less than 100 words
American National Standards Institute (ANSI) prescribes a standard SQL
Several SQL dialects exist

3. SQL Family SQL (Structured Query Language)
Data Definition Language (DDL)
CREATE
ALTER
DROP
Data Manipulation Language (DML)
SELECT
INSERT
UPDATE
DELETE
Data Control Language (DCL)
GRANT
REVOKE

4. Data Definition Commands
The database model
In this chapter, a simple database with these tables is used to illustrate commands:
CUSTOMER
INVOICE
LINE
PRODUCT
VENDOR
Focus on PRODUCT and VENDOR tables

5. Data Definition Commands (2)

6. Creating the Database Two tasks must be completed:
Create database structure
Create tables that will hold end-user data
First task:
RDBMS creates physical files that will hold database
Differs substantially from one RDBMS to another
CREATE DATABASE <DATABASENAME>;
CREATE TABLE states (
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, state CHAR(25),
population INT(9) );

7. The Database Schema Authentication
DBMS verifies that only registered users are
able to access database
Log on to RDBMS using user ID and password created by database administrator
CREATE USER IDENTIFIED BY 'password';
GRANT ALL ON db1.* TO
Schema
Group of database objects that are related to each other

8. Data Types Data type selection is usually dictated by
nature of data and by intended use
Supported data types:
Number(L,D), Integer, Smallint, Decimal(L,D)
Char(L), Varchar(L), Varchar2(L)
Date, Time, Timestamp
Real, Double, Float
Interval day to hour
Many other types

10. Creating Table Structures
Use one line per column (attribute) definition
Use spaces to line up attribute characteristics and constraints
Table and attribute names are capitalized
NOT NULL specification
UNIQUE specification
Primary key attributes contain both a NOT NULL and a UNIQUE specification
RDBMS will automatically enforce referential integrity for foreign keys
Command sequence ends with semicolon

11. Creating Table Structures (Example)

12. SQL Constraints NOT NULL constraint
Ensures that column does not accept nulls
UNIQUE constraint
Ensures that all values in column are unique
DEFAULT constraint
Assigns value to attribute when a new row is added to table. The end user may, of course, enter a value other than the default value.
CHECK constraint
Validates data when attribute value is entered

13. SQL Constraints
In this chapter, Oracle is used to illustrate SQL constraints. For example, note that the following SQL command sequence uses the DEFAULT and CHECK constraints to define the table named CUSTOMER.

14. SQL Indexes
When primary key is declared, DBMS automatically creates unique index
Often need additional indexes
Using CREATE INDEX command, SQL indexes can be created on basis of any selected attribute
Using the CREATE INDEX command, SQL indexes can be created on the basis of any selected attribute. The syntax is:
CREATE [UNIQUE] INDEX indexname ON tablename(column1 [, column2])

15. SQL Indexes
For example, based on the attribute P_INDATE stored in the PRODUCT table, the following command creates an index named P_INDATEX:
CREATE INDEX P_INDATEX ON PRODUCT(P_INDATE);
Using the UNIQUE index qualifier, you can even create an index that prevents you from using a value that has been used before. Such a feature is especially useful when the index attribute is a candidate key whose values must not be duplicated:
CREATE UNIQUE INDEX P_CODEX ON PRODUCT(P_CODE);

16. Data Manipulation Commands
INSERT
SELECT
UPDATE
DELETE
ROLLBACK
COMMIT

17. Adding Table Rows Example INSERT Used to enter data into table
Basic Syntax:
Example
INSERT INTO columnname VALUES (value1,
value2, … , valueN);
INSERT INTO VENDORVALUES (21225,'Bryson, Inc.','Smithson','615',' ','TN','Y');

18. Adding Table Rows (2) When entering values, notice that:
Row contents are entered between parentheses
Character and date values are entered between apostrophes
Numerical entries are not enclosed in apostrophes
Attribute entries are separated by commas
A value is required for each column
Use NULL for unknown values
INSERT INTO PRODUCTVALUES ('BRT-345','Titanium drill bit','18-Oct-09', 75, 10, 4.50, 0.06, NULL);

19. Saving Table Changes
Changes made to table contents are not physically saved on disk until:
Database is closed
Program is closed
COMMIT command is used
Syntax:
NOTE TO MS ACCESS USERS
MS Access doesn't support the COMMIT command because it automatically saves changes after the execution of each SQL command.
COMMIT [WORK];
Will permanently save any changes made to any table in the database

20. Listing (Showing) Table Rows
SELECT
Used to list contents of table
Basic Syntax:
SELECT columnlist FROM tablename;
Example:
SELECT * FROM PRODUCT;
Columnlist represents one or more attributes, separated by commas
Asterisk can be used as wildcard character to list all attributes

21. THE END