（1）通用语法

注释

  • 单行注释

    select database();#我是注释 select database();— 我是注释

  • 多行注释

    select database();/ 我是注释/

  1. mysql> select database();#我是注释
  2. +------------+
  3. | database() |
  4. +------------+
  5. | sys        |
  6. +------------+
  7. 1 row in set (0.00 sec)
  9. mysql> select database();-- 我是注释
  10. +------------+
  11. | database() |
  12. +------------+
  13. | sys        |
  14. +------------+
  15. 1 row in set (0.00 sec)
  17. mysql> select database();/* 我是注释*/
  18. +------------+
  19. | database() |
  20. +------------+
  21. | sys        |
  22. +------------+
  23. 1 row in set (0.00 sec)

不区分大小写

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

分号结尾

（2）SQL分类

DDL

  • Data Definition Language

  • 用来操作数据库、数据表

    DML

  • Data Manipulation Language

  • 增删改表中的数据

    DQL

  • Data Query Language

  • 查询表中的数据

    DCL

  • Data Control Language

  • 授权