Data Definition Language

Data Definition Language (DDL)

Introduction

Data Definition Language (DDL) is a subset of SQL used to define and modify the structure of a database.

DDL Commands

• CREATE: Used to create a new database object, such as a table, index, or view.
• ALTER: Used to modify the structure of an existing database object.
• DROP: Used to delete a database object.
• TRUNCATE: Used to delete all rows from a table and reset auto-incrementing IDs.

CREATE Command

• CREATE TABLE: Used to create a new table in a database.
• CREATE INDEX: Used to create an index on a table.
• CREATE VIEW: Used to create a virtual table based on a query.

ALTER Command

• ALTER TABLE: Used to modify the structure of an existing table.
• ADD COLUMN: Used to add a new column to a table.
• DROP COLUMN: Used to delete a column from a table.

DROP Command

• DROP TABLE: Used to delete a table from a database.
• DROP INDEX: Used to delete an index from a table.
• DROP VIEW: Used to delete a view from a database.

Importance of DDL

• Database Design: DDL is used to define the structure of a database.
• Database Maintenance: DDL is used to modify and maintain the structure of a database.
• Data Integrity: DDL helps ensure data integrity by defining constraints and relationships between tables.