Example sharing on mysql optimization of IN to INNER JOIN-Mysql Tutorial-php.cn

Example sharing on mysql optimization of IN to INNER JOIN

黄舟

Release： 2019-02-23 15:31:38

Original

3970 people have browsed it

When I was coding today, I encountered a SQL problem:

(recommended related mysql video tutorial: "mysql tutorial")

To match the ID of table A to the ID of table B, and query all the contents of table B:

Before optimization:

MySQL [xxuer]> SELECT 
    ->     COUNT(*)
    -> FROM
    ->     t_cmdb_app_version
    -> WHERE
    ->     id IN (SELECT 
    ->             pid
    ->         FROM
    ->             t_cmdb_app_relation UNION SELECT 
    ->             rp_id
    ->         FROM
    ->             t_cmdb_app_relation);
+----------+
| COUNT(*) |
+----------+
|      266 |
+----------+
1 row in set (0.21 sec)

Copy after login

After optimization:

MySQL [xxuer]> SELECT 
    ->     count(*)
    -> FROM
    ->     t_cmdb_app_version a
    ->         INNER JOIN
    ->     (SELECT 
    ->         pid
    ->     FROM
    ->         t_cmdb_app_relation UNION SELECT 
    ->         rp_id
    ->     FROM
    ->         t_cmdb_app_relation) b ON a.id = b.pid;
+----------+
| count(*) |
+----------+
|      266 |
+----------+
1 row in set (0.00 sec)

Copy after login

View execution plan comparison:

MySQL [xxuer]> explain SELECT 
    ->     COUNT(*)
    -> FROM
    ->     t_cmdb_app_version
    -> WHERE
    ->     id IN (SELECT 
    ->             pid
    ->         FROM
    ->             t_cmdb_app_relation UNION SELECT 
    ->             rp_id
    ->         FROM
    ->             t_cmdb_app_relation);
+----+--------------------+---------------------+-------+---------------+---------+---------+------+------+--------------------------+
| id | select_type        | table               | type  | possible_keys | key     | key_len | ref  | rows | Extra                    |
+----+--------------------+---------------------+-------+---------------+---------+---------+------+------+--------------------------+
|  1 | PRIMARY            | t_cmdb_app_version  | index | NULL          | PRIMARY | 4       | NULL |  659 | Using where; Using index |
|  2 | DEPENDENT SUBQUERY | t_cmdb_app_relation | ALL   | NULL          | NULL    | NULL    | NULL |  383 | Using where              |
|  3 | DEPENDENT UNION    | t_cmdb_app_relation | ALL   | NULL          | NULL    | NULL    | NULL |  383 | Using where              |
| NULL | UNION RESULT       | <union2,3>          | ALL   | NULL          | NULL    | NULL    | NULL | NULL | Using temporary          |
+----+--------------------+---------------------+-------+---------------+---------+---------+------+------+--------------------------+
4 rows in set (0.00 sec)

Copy after login

MySQL [xxuer]> explain SELECT 
    ->     count(*)
    -> FROM
    ->     t_cmdb_app_version a
    ->         INNER JOIN
    ->     (SELECT 
    ->         pid
    ->     FROM
    ->         t_cmdb_app_relation UNION SELECT 
    ->         rp_id
    ->     FROM
    ->         t_cmdb_app_relation) b ON a.id = b.pid;
+----+--------------+---------------------+--------+---------------+---------+---------+-------+------+--------------------------+
| id | select_type  | table               | type   | possible_keys | key     | key_len | ref   | rows | Extra                    |
+----+--------------+---------------------+--------+---------------+---------+---------+-------+------+--------------------------+
|  1 | PRIMARY      | <derived2>          | ALL    | NULL          | NULL    | NULL    | NULL  |  766 | Using where              |
|  1 | PRIMARY      | a                   | eq_ref | PRIMARY       | PRIMARY | 4       | b.pid |    1 | Using where; Using index |
|  2 | DERIVED      | t_cmdb_app_relation | ALL    | NULL          | NULL    | NULL    | NULL  |  383 | NULL                     |
|  3 | UNION        | t_cmdb_app_relation | ALL    | NULL          | NULL    | NULL    | NULL  |  383 | NULL                     |
| NULL | UNION RESULT | <union2,3>          | ALL    | NULL          | NULL    | NULL    | NULL  | NULL | Using temporary          |
+----+--------------+---------------------+--------+---------------+---------+---------+-------+------+--------------------------+
5 rows in set (0.00 sec)

Copy after login

The above is the detailed content of Example sharing on mysql optimization of IN to INNER JOIN. For more information, please follow other related articles on the PHP Chinese website!