不知道大家之前对类似MySQL通过添加索引达到优化SQL的具体操作的文章有无了解，今天我在这里给大家再简单的讲讲。感兴趣的话就一起来看看正文部分吧，相信看完MySQL通过添加索引达到优化SQL的具体操作你一定会有所收获的。
在慢查询日志中有一条慢SQL，执行时间约为3秒
mysql> SELECT -> t.total_meeting_num, -> r.voip_user_num -> FROM -> ( -> SELECT -> count(*) total_meeting_num -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND billingcode != 651158 -> AND billingcode != 651204 -> ) t, -> ( -> SELECT -> count(userID) voip_user_num -> FROM -> ( -> SELECT -> conferenceID, -> userID, -> isOnline, -> createdTime -> FROM -> ( -> SELECT -> * -> FROM -> ConferenceUser -> WHERE -> createdTime >= ADDDATE(now(), - 1) -> AND userID > 1000 -> ORDER BY -> userID, -> createdTime DESC -> ) t -> GROUP BY -> userID -> ) t, -> ( -> SELECT -> * -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND conferenceName NOT LIKE 'evmonitor%' -> ) r -> WHERE -> t.isOnline = 1 -> AND t.conferenceID = r.conferenceID -> ) r; +-------------------+---------------+ | total_meeting_num | voip_user_num | +-------------------+---------------+ | 29 | 48 | +-------------------+---------------+ 1 row in set (3.01 sec)
查看执行计划
mysql> explain SELECT -> t.total_meeting_num, -> r.voip_user_num -> FROM -> ( -> SELECT -> count(*) total_meeting_num -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND billingcode != 651158 -> AND billingcode != 651204 -> ) t, -> ( -> SELECT -> count(userID) voip_user_num -> FROM -> ( -> SELECT -> conferenceID, -> userID, -> isOnline, -> createdTime -> FROM -> ( -> SELECT -> * -> FROM -> ConferenceUser -> WHERE -> createdTime >= ADDDATE(now(), - 1) -> AND userID > 1000 -> ORDER BY -> userID, -> createdTime DESC -> ) t -> GROUP BY -> userID -> ) t, -> ( -> SELECT -> * -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND conferenceName NOT LIKE 'evmonitor%' -> ) r -> WHERE -> t.isOnline = 1 -> AND t.conferenceID = r.conferenceID -> ) r; +----+-------------+----------------+--------+----------------+----------------+---------+------+---------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+----------------+--------+----------------+----------------+---------+------+---------+---------------------------------+ | 1 | PRIMARY || system | NULL | NULL | NULL | NULL | 1 | | | 1 | PRIMARY | | system | NULL | NULL | NULL | NULL | 1 | | | 3 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 18 | | | 3 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 12667 | Using where; Using join buffer | | 6 | DERIVED | Conference | range | ind_start_time | ind_start_time | 5 | NULL | 889 | Using where | | 4 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 18918 | Using temporary; Using filesort | | 5 | DERIVED | ConferenceUser | ALL | NULL | NULL | NULL | NULL | 6439656 | Using where; Using filesort | | 2 | DERIVED | Conference | range | ind_start_time | ind_start_time | 5 | NULL | 889 | Using where | +----+-------------+----------------+--------+----------------+----------------+---------+------+---------+---------------------------------+ 8 rows in set (3.04 sec)
查看索引
mysql> show index from ConferenceUser; +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | ConferenceUser | 0 | PRIMARY | 1 | recordID | A | 6439758 | NULL | NULL | | BTREE | | | | ConferenceUser | 0 | PRIMARY | 2 | conferenceID | A | 6439758 | NULL | NULL | | BTREE | | | | ConferenceUser | 1 | ind_conference_userID | 1 | conferenceID | A | 804969 | NULL | NULL | | BTREE | | | | ConferenceUser | 1 | ind_conference_userID | 2 | userID | A | 3219879 | NULL | NULL | | BTREE | | | +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 4 rows in set (0.00 sec)
在表的列上添加索引
mysql> alter table ConferenceUser add index index_createdtime(createdTime); Query OK, 6439784 rows affected (38.46 sec) Records: 6439784 Duplicates: 0 Warnings: 0 查看索引 mysql> show index from ConferenceUser; +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | ConferenceUser | 0 | PRIMARY | 1 | recordID | A | NULL | NULL | NULL | | BTREE | | | | ConferenceUser | 0 | PRIMARY | 2 | conferenceID | A | 6439794 | NULL | NULL | | BTREE | | | | ConferenceUser | 1 | ind_conference_userID | 1 | conferenceID | A | 715532 | NULL | NULL | | BTREE | | | | ConferenceUser | 1 | ind_conference_userID | 2 | userID | A | 3219897 | NULL | NULL | | BTREE | | | | ConferenceUser | 1 | index_createdtime | 1 | createdTime | A | 6439794 | NULL | NULL | | BTREE | | | +----------------+------------+-----------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 5 rows in set (0.00 sec)
再次执行时间缩短为0.17秒
mysql> SELECT -> t.total_meeting_num, -> r.voip_user_num -> FROM -> ( -> SELECT -> count(*) total_meeting_num -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND billingcode != 651158 -> AND billingcode != 651204 -> ) t, -> ( -> SELECT -> count(userID) voip_user_num -> FROM -> ( -> SELECT -> conferenceID, -> userID, -> isOnline, -> createdTime -> FROM -> ( -> SELECT -> * -> FROM -> ConferenceUser -> WHERE -> createdTime >= ADDDATE(now(), - 1) -> AND userID > 1000 -> ORDER BY -> userID, -> createdTime DESC -> ) t -> GROUP BY -> userID -> ) t, -> ( -> SELECT -> * -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND conferenceName NOT LIKE 'evmonitor%' -> ) r -> WHERE -> t.isOnline = 1 -> AND t.conferenceID = r.conferenceID -> ) r; +-------------------+---------------+ | total_meeting_num | voip_user_num | +-------------------+---------------+ | 29 | 52 | +-------------------+---------------+ 1 row in set (0.17 sec)
查看执行计划
mysql> explain SELECT -> t.total_meeting_num, -> r.voip_user_num -> FROM -> ( -> SELECT -> count(*) total_meeting_num -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND billingcode != 651158 -> AND billingcode != 651204 -> ) t, -> ( -> SELECT -> count(userID) voip_user_num -> FROM -> ( -> SELECT -> conferenceID, -> userID, -> isOnline, -> createdTime -> FROM -> ( -> SELECT -> * -> FROM -> ConferenceUser -> WHERE -> createdTime >= ADDDATE(now(), - 1) -> AND userID > 1000 -> ORDER BY -> userID, -> createdTime DESC -> ) t -> GROUP BY -> userID -> ) t, -> ( -> SELECT -> * -> FROM -> Conference -> WHERE -> isStart = 1 -> AND startTime >= ADDDATE(now(), - 1) -> AND conferenceName NOT LIKE 'evmonitor%' -> ) r -> WHERE -> t.isOnline = 1 -> AND t.conferenceID = r.conferenceID -> ) r; +----+-------------+----------------+--------+-------------------+-------------------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+----------------+--------+-------------------+-------------------+---------+------+-------+---------------------------------+ | 1 | PRIMARY || system | NULL | NULL | NULL | NULL | 1 | | | 1 | PRIMARY | | system | NULL | NULL | NULL | NULL | 1 | | | 3 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 20 | | | 3 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 12682 | Using where; Using join buffer | | 6 | DERIVED | Conference | range | ind_start_time | ind_start_time | 5 | NULL | 879 | Using where | | 4 | DERIVED | | ALL | NULL | NULL | NULL | NULL | 18951 | Using temporary; Using filesort | | 5 | DERIVED | ConferenceUser | range | index_createdtime | index_createdtime | 4 | NULL | 31455 | Using where; Using filesort | | 2 | DERIVED | Conference | range | ind_start_time | ind_start_time | 5 | NULL | 879 | Using where | +----+-------------+----------------+--------+-------------------+-------------------+---------+------+-------+---------------------------------+ 8 rows in set (0.18 sec)
看完MySQL通过添加索引达到优化SQL的具体操作这篇文章，大家觉得怎么样？如果想要了解更多相关，可以继续关注我们的行业资讯板块。
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