1: DDL: database definition language
Used to define database objects: databases, tables, columns, etc. Keywords: create, drop, alter, etc.
2: DML: database operation language
Used to add, delete, and modify data in tables in the database. Keywords: insert, delete, update, etc.
3: DQL: database query language
Used to query records of tables in the database. Keywords: select, where
4: DCL: database control language
