SQL一对多特殊查询，取唯一一条

Posted 2020-11-28 就是你baby

转自：https://www.cnblogs.com/New-world/p/3866581.html

SQL一对多特殊查询，取唯一一条

主表：

辅表：

一个app对应多个apk，现在要取上线(Apk_Status最大的)的应用

select * from [dbo].[tbl_APP] as app 
join 

(select * from [dbo].[tbl_Apk] as AA where not exists(select top 1 * from tbl_Apk as BB where AA.Apk_APPId=BB.Apk_APPId and AA.Apk_Status < BB.Apk_Status))

 as apk on app.APP_Id = apk.Apk_APPId

重点是取关联的右表：

select * from [dbo].[tbl_Apk] as AA where not exists(select top 1 * from tbl_Apk as BB where AA.Apk_APPId=BB.Apk_APPId and AA.Apk_Status < BB.Apk_Status)

没看懂这个not exists的逻辑 ～～