SQL Basic Classification

We can classify the learned SQL language:

1. DDL: Data Definition language

A) The language of the Operation library table structure. Create Drop Alter

2. DML: Data Manipulation language

A) language of operation data: UPDATE delete insert.

3. DCL: Data Control Language

a) Operation permissions; Grant revoke

4. DQL: Data Query Language

a) Select.

Constraints on the database:

We define a table, such as a user table, a user table, some column values must be written, such as the user's name, you must write!

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SQL Basic Classification