1. Instructor: SAMIA ARSHAD
DDL COMMANDS
Instructor: SAMIA ARSHAD

2. SQL Introduction Standard language for querying and manipulating data
Structured Query Language

3. SQL Data Definition Language (DDL) Data Manipulation Language (DML)
Create/alter/delete tables and their attributes
Data Manipulation Language (DML)
Query one or more tables .
Insert/delete/modify tuples in tables.

4. Tables in SQL PName Price Category Manufacturer Hp tab 20,000 Gadgets
Table name
Attribute names
Product
PName
Price
Category
Manufacturer
Hp tab
20,000
Gadgets Hp
Ipad
40,000
Apple
Brake fluid
3,800
Automobile
Prestone
Paint
800
Household
Dulux
Tuples or rows

5. Tables Explained
The schema of a table is the table name and its attributes:
Product(PName, Price, Category, Manfacturer)
A key is an attribute whose values are unique; we underline a key

6. Data Types in SQL Atomic types:
Characters: CHAR(20), VARCHAR(50)
Numbers: INT, BIGINT, SMALLINT, FLOAT
Others: MONEY, DATETIME, …
Every attribute must have an atomic type

7. DDL commands CREATE table: used to create a table
ALTER table: modifies a table after it was created.
DROP table: removes a table from a database

8. CREATE TABLE CREATE TABLE employee (Employeeid INT,ENAME VARCHAR(50),
JOB VARCHAR(80))
SETTING PK
(Employeeid INT PRIMARY KEY,ENAME VARCHAR(50),
JOB VARCHAR(80)))

9. Alter
ALTER TABLE statement is used to add, modify, or drop/delete columns in a table.
To ADD A COLUMN in a table:
ALTER TABLE employee
ADD salary int(45);

10. ADD MULTIPLE COLUMNS IN TABLE
ALTER TABLE employee
ADD (employee_firstname varchar(45), city varchar(40));
MODIFY COLUMN IN TABLE
MODIFY CITY CHAR

11. DROP To delete a column in a table, use the following syntax.
ALTER TABLE table_name DROP COLUMN column_name
ALTER TABLE employee
DROP COLUMN city

12. DROP TABLE
To delete a table from database.
DROP TABLE table_name