取A表数据，关联B表任意一条数据

 表A===================

AID, AName

1 jack

2 mary

3 lily

表B==================

BID, AID, BName

1 1 aaa

2 1 bbb

3 1 ccc

4 2 ddd

5 2 eee

一、sql语句==============

--A 表数据

select  * from A_TB

--B 表数据

select  * from B_TB

--结果：取A表数据，关联B表任意一条数据

select  * from A_TB

left join (select MAX(BID)bid,MAX(BName)bname,AID from B_TB group by AID)b on A_TB.AID=b.AID

二、结果==================

AID ,  AName, Bid,BName

1 jack 3 ccc 1

2 mary 5 eee 2

3 lily NULL NULL NULL

另外一种方法======

select * from (

select a.*,(select top 1 Id from B as b where b.CgId =a.ID)as bid

from A as a) as temp

left join B as b2 on temp.bid=b2.Id