SQL- DDL, DML, DCL, DTL, DQL- SQL Commands With Examples SQL, Structured Query Language, is a programming language designed to manage data stored in relational databases. SQL Commands:- SQL commands are instructions. It is used to communicate with the database. Types of SQL Commands:- Data Definition Language (DDL):- DDL changes the structure of the table like creating a table, deleting a table, altering a table, etc.