SQL Commands: DDL, DML, and DCL

Question

ICSM Computer · Answer

1. What is DDL (Data Definition Language)?

DDL commands are used to define and manage the structure of the database (schema). These commands deal with tables, indexes, and database objects.

CREATE TABLE Users (
    Id INT PRIMARY KEY,
    Name VARCHAR(100)
);

Key Point:
DDL commands automatically commit changes (cannot rollback easily).

Answer:
DML commands are used to manipulate data inside tables.

INSERT INTO Users (Id, Name)
VALUES (1, 'John');

Key Point:

DCL commands are used to control access and permissions in the database.

GRANT SELECT ON Users TO User1;

Key Point:
Used for security and authorization

Feature	DDL	DML	DCL
Purpose	Define structure	Manage data	Control access
Works On	Tables, schema	Records (rows)	Users & permissions
Commands	CREATE, ALTER, DROP	INSERT, UPDATE, DELETE	GRANT, REVOKE
Rollback	No (auto commit)	Yes	Depends

If asked in interview, answer like this:

“DDL is used to define database structure, DML is used to manipulate data, and DCL is used to control access and permissions.”