取时间最大的一条记录

A表
id          title
a1            a1

b表
id          Aid      name      time
b1         a1         u             2017-5-6
b2         a1         x              2017-7-8

b3         a1         z              2017-2-9

显示成

b2 a1 x 2017-07-08 

if not object_id(N'Tempdb..#A') is null
    drop table #A
Go
Create table #A([id] nvarchar(22),[title] nvarchar(22))
Insert #A
select N'a1',N'a1'
GO
if not object_id(N'Tempdb..#B') is null
    drop table #B
Go
Create table #B([id] nvarchar(22),[Aid] nvarchar(22),[name] nvarchar(21),[time] DateTIME)
Insert #B
select N'b1',N'a1',N'u','2017-5-6' union all
select N'b2',N'a1',N'x','2017-7-8' union all
select N'b3',N'a1',N'z','2017-2-9'
Go
select * from  #A
select * from  #B


;WITH cte AS (
SELECT  * ,
        ROW_NUMBER() OVER ( PARTITION BY Aid ORDER BY time DESC ) AS num
FROM    #B 
)
SELECT  cte.id ,
        cte.Aid ,
        cte.name ,
        cte.time
FROM    cte
        JOIN #A ON #A.id = cte.Aid
WHERE   cte.num = 1;