Question

我有一个方案来获取“Max”和“Min”记录的相应字段值请在下面找到示例数据

-----------------------------------------------------------------------
ID             Label             ProcessedDate
-----------------------------------------------------------------------
1              Label1            11/01/2016
2              Label2            11/02/2016
3              Label3            11/03/2016
4              Label4            11/04/2016
5              Label5            11/05/2016

我将另一个表中填充的“ID”字段作为外键。在根据“ID”字段查询该表中的那些记录时，我需要获取“最大”处理日期和“最小”处理日期的“标签”字段。

 -----------------------------------------------------------------------
    ID      LabelID      GroupingField
 -----------------------------------------------------------------------
    1       1            101
    2       2            101
    3       3            101
    4       4            101
    5       5            101
    6       1            102
    7       2            102
    8       3            102
    9       4            102

最后的结果集我希望它看起来像这样。

 -----------------------------------------------------------------------
   GroupingField         FirstProcessed         LastProcessed
 -----------------------------------------------------------------------
   101                   Label1                 Label5
   102                   Label1                 Label4

我已经“差点”设法使用等级函数获得上述结果，但仍然不满意。所以我在寻找是否有人可以为我提供更好的选择。

谢谢， Prakazz

Answer 1

    CREATE TABLE #Details (ID INT,LabelID INT,GroupingField INT)
CREATE TABLE #Details1 (ID INT,Label VARCHAR(100),ProcessedDate VARCHAR(100)) 

INSERT INTO #Details1 (ID ,Label ,ProcessedDate )
SELECT 1,'Label1','11/01/2016' UNION ALL
SELECT 2,'Label2','11/02/2016' UNION ALL
SELECT 3,'Label3','11/03/2016' UNION ALL
SELECT 4,'Label4','11/04/2016' UNION ALL
SELECT 5,'Label5','11/05/2016'


INSERT INTO #Details (ID ,LabelID ,GroupingField )
SELECT 1,1,101 UNION ALL
SELECT 2,2,101 UNION ALL
SELECT 3,3,101 UNION ALL
SELECT 4,4,101 UNION ALL
SELECT 5,5,101 UNION ALL
SELECT 6,1,102 UNION ALL 
SELECT 7,2,102 UNION ALL
SELECT 8,3,102 UNION ALL
SELECT 9,4,102

;WITH CTE (GroupingField , MAXId ,MinId) AS
(
    SELECT GroupingField,MAX(LabelID) MAXId,MIN(LabelID) MinId
    FROM #Details
    GROUP BY GroupingField  
)


SELECT GroupingField ,B.Label FirstProcessed, A.Label LastProcessed
FROM CTE
JOIN #Details1 A ON MAXId = A.ID
JOIN #Details1 B ON MinId = B.ID

Answer 2

您可以使用分区依据的SQL Row_Number（）函数，如下所示，使用分组依据

;with cte as (
    select 
        t.Label, t.ProcessedDate,
        g.GroupingField,
        ROW_NUMBER() over (partition by GroupingField Order By ProcessedDate ASC) minD,
        ROW_NUMBER() over (partition by GroupingField Order By ProcessedDate DESC) maxD

    from tbl t 
    inner join GroupingFieldTbl g
    on t.ID = g.LabelID
 )
select GroupingField, max(FirstProcessed) FirstProcessed, max(LastProcessed) LastProcessed
from (
select
     GroupingField,
     FirstProcessed = CASE when minD = 1 then Label else null end,
     LastProcessed = CASE when maxD = 1 then Label else null end
from cte 
where 
    minD = 1 or  maxD = 1
) t
group by GroupingField
order by GroupingField

我还使用CTE表达式使编码更容易理解

输出为

最大值和最小值的相应记录

2 个答案: