我有以下查询:
SELECT COUNT(DISTINCT(`person_id`)) as `count`, `mc_office`.`name` as `office_name`
FROM `aft_people`
INNER JOIN `aft_offices`
ON `aft_people`.`lc`=`aft_offices`.`id`
INNER JOIN `aft_offices` as `mc_office`
ON `aft_offices`.`parent_id` = `mc_office`.`id`
INNER JOIN `aft_constant_maps` as `constant_maps`
ON `aft_people`.`person_id` = `constant_maps`.`representable_id`
WHERE `constant_maps`.`constant_id` IN (741)
GROUP BY `mc_office`.`name`
表 aft_people 有 1M 条记录,aft_constant_maps 有大约 5M 条记录。 字段上有索引
- aft_people.person_id
- aft_constant_maps.representable_id
- aft_constant_maps.constant_id
查询真的非常慢,有时甚至根本无法加载。我需要在 10 秒内执行此查询。
如果您需要更多信息来帮助我,请告诉我。
最佳答案
对于这个查询(我刚刚重新排列了连接,以便我可以更好地跟踪它们):
SELECT COUNT(DISTINCT(`person_id`)) as `count`,
`mc_office`.`name` as `office_name`
from `aft_people` INNER JOIN
`aft_constant_maps` as `constant_maps`
ON `aft_people`.`person_id` = `constant_maps`.`representable_id` INNER JOIN
`aft_offices`
ON `aft_people`.`lc` = `aft_offices`.`id` INNER JOIN
`aft_offices` as `mc_office`
ON `aft_offices`.`parent_id` = `mc_office`.`id`
WHERE `constant_maps`.`constant_id` IN (741)
GROUP BY `mc_office`.`name`
最好的索引是:constant_maps(constant_id,representable_id)
、aft_people(person_id, lc)
和aft_offices(id,parent_id)
。这些可能有助于加快查询速度。
关于mysql - 使用多个内连接加速 SQL 查询,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29431203/