[英]Select distinct rows whilst grouping by max value
我目前有下表:
ID | Name | EventTime | State
1001 | User 1 | 2013/07/22 00:00:05 | 15
1002 | User 2 | 2013/07/23 00:10:00 | 100
1003 | User 3 | 2013/07/23 06:15:31 | 35
1001 | User 1 | 2013/07/23 07:13:00 | 21
1001 | User 1 | 2013/07/23 08:15:00 | 25
1003 | User 3 | 2013/07/23 10:00:00 | 22
1002 | User 2 | 2013/07/23 09:18:21 | 50
我需要的是上一个eventtime
每个不同userid
的state
,类似于下面的:
ID | Name | EventTime | State
1001 | User 1 | 2013/07/23 08:15:00 | 25
1003 | User 3 | 2013/07/23 10:00:00 | 22
1002 | User 2 | 2013/07/23 09:18:21 | 50
我需要类似下面的东西,但我不能得到我需要的东西。
SELECT ID, Name, max(EventTime), State
FROM MyTable
GROUP BY ID
SELECT
ID, Name, EventTime, State
FROM
MyTable mt
WHERE EventTime = (SELECT MAX(EventTime) FROM MyTable sq WHERE mt.ID = sq.ID)
在支持分析函数的数据库中,您可以使用row_number()
:
select *
from (
select row_number() over (partition by ID
order by EventTime desc) as rn
, *
from YourTable
) as SubQueryAlias
where rn = 1
您没有指定正在使用的数据库,但是您应该能够在子查询中使用聚合函数来获取每个id的最大事件时间:
select t1.id,
t1.name,
t1.eventtime,
t1.state
from mytable t1
inner join
(
select max(eventtime) eventtime, id
from mytable
group by id
) t2
on t1.id = t2.id
and t1.eventtime = t2.eventtime
order by t1.id;
你可以试试这个: -
SELECT ID, Name, EventTime, State
FROM mytable mm Where EventTime IN (Select MAX(EventTime) from mytable mt where mt.id=mm.id)
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