What are DDL, DML, DCL, TCL?

These are classes of SQL commands that group database operations by purpose:

#1. DDL (Data Definition Language)

Used to create and change the database's structure. Example commands:

• CREATE TABLE, create a table
• ALTER TABLE, change a table (add a column, change a data type)
• DROP TABLE, delete a table

The gist: manages structure, not data.

#2. DML (Data Manipulation Language)

Used to add, change, delete, and retrieve data. Example commands:

• SELECT, retrieve data
• INSERT, insert a new record
• UPDATE, change an existing record
• DELETE, delete a record

The gist: works with the actual data inside tables.

#3. DCL (Data Control Language)

Used to manage user rights and security. Example commands:

• GRANT, give a user rights
• REVOKE, take rights away

The gist: controls who's allowed to do what in the database.

#4. TCL (Transaction Control Language)

Used to manage the logic of running groups of operations (transactions). Example commands:

• COMMIT, confirm changes
• ROLLBACK, undo changes
• SAVEPOINT, create a save point inside a transaction

The gist: ensures data integrity when several operations run at once.