SQL language Classification and writing rules

1. Data Query Language (SELECT statement): for retrieving database data

2. Data manipulation language (manipulation Language,dml): Used to change database data, including insert,update and delete three statements

3. Transaction control Language (transactional Controls LANGUAGE,TCL): For maintaining data consistency,

including Commit, Rollback and SavePoint three statements. Where a commit statement is used to confirm that a database change has been made, the rollback statement is used to cancel a database change, and the savepoint statement is used to set the savepoint to cancel some of the database changes.

4. Data definition Language (LANGUAGE,DDL): Used to create, modify, and delete database objects

The DDL statement automatically commits the transaction.

5. Data Control LANGUAGE,DCL: Used to perform permission grant and retract operations, including GRANT and revoke two commands, where the grant command grants permissions to a user or role, and The revoke command is used to retract the permissions that a user or role has. The DCL statement automatically commits the transaction.

Rules:

The 1.sql keyword is case-insensitive, can be used in uppercase or lowercase format, or in a mixed case format.

2. Object and column names are case-insensitive, either in uppercase or lowercase format, or in a mixed case format.

3. Character values and date values are case-sensitive