最全MySQL8.0实战教程 22 MySQL的优化 22.4 explain分析执行计划 22.4.3 Explain之select_type

「爱情、让人受尽委屈。」 2024-03-25 09:26 105阅读 0赞

#### 最全MySQL8.0实战教程 ####

#### 文章目录 ####

*   *   *  最全MySQL8.0实战教程
         *  22 MySQL的优化
         *   *  22.4 explain分析执行计划
             *   *  22.4.3 Explain之select\_type

[【黑马程序员MySQL知识精讲+mysql实战案例\_零基础mysql数据库入门到高级全套教程】 ][MySQL_mysql_mysql_]

#### 22 MySQL的优化 ####

##### 22.4 explain分析执行计划 #####

###### 22.4.3 Explain之select\_type ######

表示 SELECT 的类型，常见的取值，如下表所示：

![在这里插入图片描述][b7a72853991f4f99a8c521fe4bf11f71.png_pic_center]

-- SIMPLE
    explain select * from user;

![在这里插入图片描述][2f300361729a4a3093f984698391cd11.png_pic_center]

-- PRIMARY【主查询】
    explain select * from role where rid = (select rid from user_role where uid = (select uid from user where uname = '张飞'));

![在这里插入图片描述][d47fd1e810ab4bd3bf37bcc198fe252b.png_pic_center]

子查询

![在这里插入图片描述][c1f13eda1e7f4e9798999aae62570d3f.png_pic_center]

-- DERIVED
    explain select * from (select * from user limit 2) t;

![在这里插入图片描述][94759647abc249e7b9a19a43d2b0d0fe.png_pic_center]

-- UNION / UNION RESULT
    explain select * from user where uid = 1 union select * from user where uid = 3;

![在这里插入图片描述][4e4b76d108f844adb732bc1d645de0f0.png_pic_center]

[MySQL_mysql_mysql_]: https://www.bilibili.com/video/BV1iF411z7Pu
[b7a72853991f4f99a8c521fe4bf11f71.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/4eff31ae074049178d265106c5b97ace.png
[2f300361729a4a3093f984698391cd11.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/5114063543ee4a8faf7f14a0d9122230.png
[d47fd1e810ab4bd3bf37bcc198fe252b.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/6c27d5ab769f41e6b13d772dbfd8e83c.png
[c1f13eda1e7f4e9798999aae62570d3f.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/746054f832cd45f7930385efc4f584bf.png
[94759647abc249e7b9a19a43d2b0d0fe.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/e36a1b6a21f84097a539f775d450af05.png
[4e4b76d108f844adb732bc1d645de0f0.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/91fd03d41b6540b2b134e7292aa68e7e.png