mysql order by 造成語句 執行計划中Using filesort,Using temporary相關語句的優化解決

mysql> explain  select permission.* from t_rbac_permission   permission  inner JOIN  t_rbac_acl  acl  on acl.PERMISSION_ID=permission.ID

 where  permission.menu=1 and acl.PRINCIPAL_TYPE=0     order by permission.create_date desc;

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+----------------------------------------------+

| id | select_type | table      | type   | possible_keys      | key     | key_len | ref                         | rows | Extra                                        |

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+----------------------------------------------+

|  1 | SIMPLE      | acl        | ALL    | FKE43AF088F9936F96 | NULL    | NULL    | NULL                        |   94 |  Using where; Using temporary; Using filesort |

|  1 | SIMPLE      | permission | eq_ref | PRIMARY            | PRIMARY | 98      | bs_common.acl.PERMISSION_ID |    1 | Using where                                  |

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+----------------------------------------------+

2 rows in set (0.00 sec)

 

 

 

 explain  select permission.* from t_rbac_permission   permission  inner JOIN  t_rbac_acl  acl

    on acl.PERMISSION_ID=permission.ID   where   permission.menu=1 and acl.PRINCIPAL_TYPE=0      ;

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+-------------+

| id | select_type | table      | type   | possible_keys      | key     | key_len | ref                         | rows | Extra       |

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+-------------+

|  1 | SIMPLE      | acl        | ALL    | FKE43AF088F9936F96 | NULL    | NULL    | NULL                        |   94 |  Using where |

|  1 | SIMPLE      | permission | eq_ref | PRIMARY            | PRIMARY | 98      | bs_common.acl.PERMISSION_ID |    1 | Using where |

+----+-------------+------------+--------+--------------------+---------+---------+-----------------------------+------+-------------+

 

 

？？？？？ why    加上   order by permission.create_date desc 的影響？？？ 

 首先查看相關字段是否加上索引如 order by的字段是否加上索引。加上索引之后單表查詢看如何？？

 

 

 

 

 

 ok 單表查詢還是Using filesort. 查詢相關資料進行組合索引試試看

 

 

ok，現在終結了，那么試試連接查詢。各種測試結果如下： 

 

 

 

例如：

 

增加索引后

 

效果如下