SQL statements are mainly divided into three categories:
DDL (Data Definition Languages) statement: data definition language . These statements define the different segments of data, databases, tables, columns, indexes, and other database objects. Commonly used keywords including create, drop, alter and so on .
DML (Data Manipulation Language) statement: data manipulation language . Used to add, delete, update and query database records, and to check data integrity. Commonly used sentence keywords mainly include Insert, delete, and update.
DCL (Data Control Language) statement: data control statement . Statements used to control the direct permissions and access levels of different data segments. These statements define the access rights and security levels of databases, tables, fields, and users. The main statement keywords include grant, revoke and so on .