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 ～～SQL一对多特殊查询，取唯一一条,布布扣,bubuko.com
原文：http://www.cnblogs.com/New-world/p/3866581.html