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mysql5.7版本的explain解析

先在mysql中建个表:

 CREATE   TABLE   `t_user`  (
  `id`   int ( 6 )  NOT   NULL   AUTO_INCREMENT,
  `name`   varchar ( 30 )  CHARACTER   SET  latin1 COLLATE latin1_swedish_ci  NOT   NULL  ,
  `age`   int ( 4 )  NOT   NULL   DEFAULT   20  ,
  `address`   varchar ( 30 )  CHARACTER   SET  latin1 COLLATE latin1_swedish_ci  NOT   NULL default ‘‘  ,
  `create_time`   datetime   NOT   NULL   DEFAULT   CURRENT_TIMESTAMP  ,
  `version`   int ( 4 )  NOT   NULL   DEFAULT   0  ,
     PRIMARY   KEY     (`id`) USING BTREE ,
     UNIQUE   INDEX     `idx_name`(`name`) USING BTREE ,
    INDEX    `idx_age_address`(`age`, `address`) USING BTREE 
) ENGINE   =  InnoDB AUTO_INCREMENT  =   15   CHARACTER   SET   =  latin1 COLLATE  =  latin1_swedish_ci ROW_FORMAT  =  DYNAMIC;

这个DDL创建了3个B+tree索引,我都用黄色背景标出来了。现在开始使用explain对各种查询进行分析:

 

1、type = ALL 是全表扫描

EXPLAIN select * from t_user; -- 全表扫描

 

 

 

 

 

 

end.

 

mysql5.7版本的explain解析

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