Table1
ID SN
1 AAAAA
2 BBBBB
3 CCC
Table2
ID TIME
1 2017.3.20
1 2017.3.21
1 2017.3.22
2 2017.4.20
2 2017.4.21
2 2017.4.22
3 2017.4.22
表1和表2的 ID 是关联的，表2的每个ID可能有多条记录，但是TIME列的值不同的。
要求输入多个SN，查询结果要求按时间排序，一个SN只保留最后一个日期的一条记录：
ID SN TIME
1 AAAAA 2017.3.22
2 BBBBB 2017.4.22
3 CCC 2017.4.22
select max(t2.id) as id,(select t1.sn from table1 t1 where t1.id =max(t2.id) as sn,max(t2.time) as time from table2 t2 group by t2.id;
SELECT dbo.Table_1.Id, dbo.Table_1.SN, MAX(dbo.Table_2.Time) FROM dbo.Table_2 INNER JOIN dbo.Table_1 ON Table_1.Id = Table_2.Id
GROUP BY dbo.Table_1.Id, dbo.Table_1.SN, dbo.Table_2.Id
select sn,(select max(time) from table2 where id = q.id ) from table1 q
select * from table2 t2 left join table1 t1 on t2.id=t1.id
where t1.sn=''
order by t2.time desc
select table2.sn from table1 left join (select max(time) sn,id from table2) table2 on table2.id=table1.id
select table2.sn from table1 left join (select max(time) sn,id from table2) table2 on table2.id=table1.id order by table2.sn desc