我有一个很长的查询，其中有多个联接已超时。我已经在所有发起人表中创建了Sponsor_Id（在WHERE中使用）作为索引。探查器图表显示了惊人的缓慢性（发送数据的时间为75％）。
这是查询：
SELECT GROUP_CONCAT(DISTINCT masterdetail.eventid) as eventids
FROM tblsponsor_slave_eventprefrencesdetail userprefrence
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_category
userprefcategory
ON userprefrence.SponsorId = userprefcategory.SponsorId
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_locationtarget
userpreflocation
ON userprefrence.SponsorId = userpreflocation.SponsorId
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_type userprefEventType
ON userprefrence.SponsorId = userprefEventType.SponsorId
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_audienceprofile
userprefAudiProfile
ON userprefrence.SponsorId = userprefAudiProfile.SponsorId
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_industry
userprefIndustry
ON userprefrence.SponsorId = userprefIndustry.SponsorId
INNER JOIN tblsponsor_slave_eventprefrencesdetail userprefdetail
ON userprefrence.SponsorId = userprefdetail.SponsorId
INNER JOIN tblsponsor_slave_sponsor_eventprefrence_audiencetype
userprefAudiType
ON userprefrence.SponsorId = userprefAudiType.SponsorId
INNER JOIN tblsponsor_slave_eventprefrence_agegroup userprefAgeGroup
ON userprefrence.SponsorId = userprefAgeGroup.SponsorId
INNER JOIN tblevent_slave_event_address_city eventcity
ON userpreflocation.Sponsor_EventPrefrence_LocationTarget =
eventcity.Event_Address_City
INNER JOIN tblevent_slave_event_audienceprofile eventAudiProfile
ON userprefAudiProfile.Sponsor_EventPrefrence_AudienceProfile =
eventAudiProfile.Event_AudienceProfile
INNER JOIN tblevent_slave_event_industrycatered eventindustry
ON userprefIndustry.Sponsor_EventPrefrence_Industry =
eventindustry.Event_IndustryCatered
INNER JOIN tblevent_slave_agegroup eventagegroup
ON userprefAgeGroup.Sponsor_AgeGroup_Type =
eventagegroup.Event_AgeGroup_Type
AND userprefAgeGroup.IsExist = eventagegroup.IsExist
INNER JOIN tblevent_master_detail masterdetail
ON eventcity.EventId = masterdetail.EventId
INNER JOIN tblevent_slave_others eventothers
on masterdetail.EventId = eventothers.EventId
AND masterdetail.Event_Category =
userprefcategory.Sponsor_EventPrefrence_Category
AND masterdetail.Event_Type =
userprefEventType.Sponsor_EventPrefrence_Type
AND eventothers.Event_Gender =
userprefdetail.Sponsor_EventPrefrence_Gender
AND eventothers.Event_TargetAudience =
userprefAudiType.Sponsor_EventPrefrence_AudienceType
AND eventothers.Event_Sponsor_Range_Min <
userprefrence.Sponsor_EventPrefrence_Range_Max
WHERE userprefrence.SponsorId = 164
AND eventagegroup.IsExist = 1
AND masterdetail.Event_StartDateTime > '2015-08-27'
AND masterdetail.Event_Category in ( "1", "2", "3", "7",
"9", "10", "11" )
AND eventcity.Event_Address_City in ( "1", "3", "54" )
AND masterdetail.Event_Type in ( "2", "3", "4", "5", "7" )
AND eventindustry.Event_IndustryCatered in ( "13", "18" )
AND eventAudiProfile.Event_AudienceProfile in ( "1", "2", "10" )
最佳答案
优化器将（可能）从以WHERE子句中的内容进行最佳过滤的表开始。哪个看起来最有选择性？假设它是masterdetail.Event_StartDateTime > '2015-08-27'。然后，您需要在masterdetail上以Event_StartDateTime开头的索引。
然后它将移至其他表。它可能会看到：
ON eventcity.EventId = masterdetail.EventId
暗示
eventcity是下一张表，它需要某种方式。闻起来像EventId是PRIMARY KEY;因此无需采取进一步措施。然后转到下一张表。接下来。等等。
这些
WHERE子句需要一些讨论：userprefrence.SponsorId = 164
eventagegroup.IsExist = 1
它们是column =常数，这使它们非常适合索引。另一方面，
IsExist闻起来像是对/错标志，它本身在索引中几乎永远不会有用。无论如何，对于包含字段和
JOINed处于打开状态的字段，使用复合索引可能会很有用。您能证明15个表格的
JOIN吗？好多（“规范化，但不要过度规范化。”）我视而不见-能否为每个人提供
SHOW CREATE TABLE（在实施我的建议之后）？我给你的可能不是所有可以做的。
sending data是无用的信息；他们需要以某种方式将其分解。