SQL classification

The SQL language is mainly divided into the following three categories in terms of functions:
       1. DDL (Data Definition Languages, Data Definition Language) , these statements define different database objects such as databases, tables, views, indexes, etc., and can also be used to create and delete. , Modify the structure of the database and data tables.
       The main statement keywords include CREATE, DROP, ALTER , etc.

       2, DML (Data Manipulation Language, Data Manipulation Language) , used to add, delete, update and query database records, and check data integrity.
       The main statement keywords include INSERT, DELETE, UPDATE, SELECT , etc.

       3. DCL (Data Control Language, Data Control Language) , used to define the access rights and security levels of databases, tables, fields, and users.
       The main statement keywords include GRANT, REVOKE, COMMIT, ROLLBACK, SAVEPOINT , etc.