Question

我目前正在使用pivot，unpivot检索最后6个可用日期数据。任何人都可以帮我解决这个问题吗？

select * 
from #myTable
unpivot (value for Area in (abc,def,fgh,ijk,klp)) up
pivot (max(value) for [date] in (
##-- Here I need to get the last 6 available dates less than current date
)) p

[Date]列的数据类型为DATE.

我的数据库中的日期示例值

2017-09-16,
2017-09-09,
2017-09-02,
2017-08-26,
2017-07-22,
2017-07-01,
2017-06-24,
2017-06-11

Sample table, with expected result

Answer 1

那么，根据您的样本数据，每个区域的一个区域的前6个是相同的，因为Area是列名称。有了这些信息，我们可以在原始数据透视后使用动态unpivot。

declare @table table (TheDate date, abc int, def int, fgh int, ijk int, klp int)
insert into @table
values
('20170916',1,2,34,4,5),
('20170909',2,3,4,5,676),
('20170902',6,7,8,8,9)

DECLARE @DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE @ColumnName AS NVARCHAR(MAX)

if object_id('tempdb..#staging') is not null drop table #staging

select
    Area
    ,TheDate
    ,Val
into #staging
from @table
unpivot 
    (Val for Area in (abc,def,fgh,ijk,klp)
    ) up


--Get distinct values of the PIVOT Column / top 6 by date
SELECT @ColumnName= ISNULL(@ColumnName + ',','') 
       + QUOTENAME(TheDate)
FROM (SELECT DISTINCT TOP 6 TheDate FROM #staging ORDER BY TheDate DESC) AS TheDate

--Prepare the PIVOT query using the dynamic 
SET @DynamicPivotQuery = 
  N'SELECT Area, ' + @ColumnName + '
    FROM #staging
    PIVOT(SUM(Val) 
          FOR TheDate IN (' + @ColumnName + ')) AS PVTTable'

--Execute the Dynamic Pivot Query
EXEC sp_executesql @DynamicPivotQuery

<强> See It In Action Here

枢轴＆amp; UnPivot功能与SQL Server中的日期

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