DDL – Data Definition Language
These are used to create and manage the structure of objects within a database. For example, CREATE, DROP, ALTER commands ON tables, views, indexes, keys…
DML – Data Manipulation Language
These are the commands used to actually query, modify and delete data within a database. For example SELECT, INSERT, UPDATE, DELETE.
DCL – Data Control Language
These are used to control access to databases and objects. For example GRANT, REVOKE, DENY
TCL – Transactional Control Language
These are used to control data modifications made my transactions. For example ROLLBACK TRANSACTION, BEGIN TRANSACTION, COMMIT TRANSACTION