If you look at the large variety of SQL commands, they can be divided into three large subgroups. Data
Definition Language deals with database schemas and descriptions of how the data should reside in the
database, therefore language statements like CREATE TABLE or ALTER TABLE belong to DDL.
DML deals with data manipulation, and therefore includes most common SQL statements such
SELECT, INSERT, etc. Data Control Language includes commands such as GRANT, and mostly
concerns with rights, permissions and other controls of the database system.