IN에서 INNER JOIN으로의 mysql 최적화 공유 예

오늘 코딩을 하다가 SQL 문제가 발생했습니다.

(추천 관련 mysql 동영상 튜토리얼: "mysql tutorial")

테이블 A의 ID를 테이블 B의 ID와 일치시키려면 테이블 B의 ID 모든 내용 쿼리:

최적화 전:

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)

최적화 후:

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)

실행 계획 비교 보기:

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)

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)

위 내용은 IN에서 INNER JOIN으로의 mysql 최적화 공유 예의 상세 내용입니다. 자세한 내용은 PHP 중국어 웹사이트의 기타 관련 기사를 참조하세요!