🏗️ DDL (Data Definition Language) in SQL

Last Updated: January 2026

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DDL (Data Definition Language) is a category of SQL commands used to define, create, modify, and delete database structures.

👉 DDL works on schema / structure, not on table data.

• Create tables and databases
• Modify table structure
• Remove tables or schemas
• Define columns, data types, constraints

Hinglish Tip 🗣: Database ka structure banana ya badalna ho → DDL commands use hote hain.

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🧩 DDL Commands

We will cover each command in a separate tutorial. Here is just the big picture 👇

CREATE

• Used to create database objects
• Tables, databases, views, indexes

CREATE TABLE table_name (...);

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ALTER

• Used to modify existing table structure
• Add / drop / change columns

ALTER TABLE table_name ADD column datatype;

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DROP

• Used to permanently delete database objects
• Table structure + data both removed

DROP TABLE table_name;

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TRUNCATE

• Used to remove all data from a table
• Structure remains

TRUNCATE TABLE table_name;

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ALTER TABLE

• Used to rename table or object
• Not supported in same way by all DBs

RENAME TABLE old_name TO new_name;

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