SQL按日期分组

Question

我正在尝试将此结果分组：

ID  TEXT             Table1  FK1    Nodedate
940 bov1             TASKS   48  2016-10-26 15:53:20.247
938 foxxxxdsx        TASKS   48  2016-10-26 15:49:15.083
937 test2            TASKS   48  2016-10-26 15:24:32.667
936 test             TASKS   48  2016-10-26 15:24:20.277
889 <>asdasdsa       TASKS   48  2016-09-19 11:23:02.083
600 sadadasasdadsa   TASKS   48  2016-08-29 15:03:11.680

变成公正

ID  TEXT             Table1  FK1    Nodedate
940 bov1             TASKS   48  2016-10-26 15:53:20.247

有没有一种方法可以只用日期将结果分组？

当前查询：

SELECT  N.ID As ID , n.Text as Text ,Table1 , FK1 ,N.Created as notedate 
FROM NOTES N With(nolock)
LEFT OUTER JOIN NOTELinks NL On(N.id = NL.noteid)
WHERE Table1 = 'TASKS' AND N.IsSystem =0 AND FK1=48  
GROUP BY Table1 , FK1 
order by N.Created desc

Answer 1

您是否只想要最新记录？

SELECT TOP 1
    N.ID As ID,
    N.Text AS Text,
    Table1,
    FK1,
    N.Created AS notedate 
FROM NOTES N WITH (NOLOCK)
LEFT JOIN NOTELinks NL
    ON N.id = NL.noteid
WHERE
    Table1 = 'TASKS' AND
    N.IsSystem = 0   AND
    FK1 = 48
ORDER BY N.Created DESC

如果需要查找每个Table1和FK1组的最新记录，请考虑使用分析函数：

SELECT t.ID, t.Text, t.Table1, t.FK1, t.notedate
FROM
(
    SELECT TOP 1 N.ID As ID, N.Text as Text, Table1, FK1, N.Created AS notedate,
        RANK() OVER (PARTITION BY Table1, FK1 ORDER BY N.Created DESC) rank
    FROM NOTES N With(nolock)
    LEFT JOIN NOTELinks NL
        ON N.id = NL.noteid
    WHERE Table1 = 'TASKS' AND N.IsSystem = 0 AND FK1 = 48
) t
WHERE t.rank = 1;

如果两个或多个记录可能是最新记录，那么我在这里使用RANK而不是ROW_NUMBER 。 在这种情况下，以上查询将返回所有联系。

Answer 2

我建议使用ROW_NUMBER() ，因为如果要求超过1个FK1 ，或者您需要一个OFFSET ，则无法使用TOP来完成：

SELECT p.* FROM (
    SELECT .....
           ROW_NUMBER() OVER(PARTITION BY n.FK1 ORDER BY n.created DESC) as rnk
    FROM .... // REST OF THE QUERY ) p
WHERE p.rnk = 1

动态返回每个FK1存在的所有最新记录