Four components of SQL language

1. The data definition language DDL: used to define the logical structure of the database, including databases, base tables, indexes and views, defined extended DDL supports stored procedures, functions, objects, triggers the like. DDL include three languages, namely to define, modify and delete;

2. Data Manipulation Language DML: mainly used for data retrieval and updating the database, wherein the update operation comprises insert, delete and modify data;

3. Data Control Language DCL: mainly used for object database authorization, user maintenance (including create, modify and delete), and transaction integrity rules defined definitions;

4. Other: Embedded SQL language and dynamic language.