MySQL 同一结果，采用不同命令有天壤之别

比较了两条 MySQL 命令，差异巨大。看来要小心 IN 子句！

SELECT DISTINCT a.FamilyID,a.GenusID,a.SPID,a.FamilyName,a.CFamilyName,a.GenusName,a.CGenusName,a.LName,a.CName
From IDents a,(select DISTINCT SPID from Photo Where FolderID='5bbb2ae0-a747-4f3c-afce-3ed39f784f56' AND LName!='') AS b
Where a.SPID=b.SPID

执行时间 0.0132s

SELECT DISTINCT a.FamilyID,a.GenusID,a.SPID,a.FamilyName,a.CFamilyName,a.GenusName,a.CGenusName,a.LName,a.CName
From IDents a
Where a.SPID IN
(select DISTINCT SPID from Photo Where FolderID='5bbb2ae0-a747-4f3c-afce-3ed39f784f56' AND LName!='')

执行时间 76.1623s