sql-server - 为什么此 T-SQL 查询会抛出 "aggregate function"错误消息？

Question

我正在使用 SQL Server 2014，并且我有以下 SQL 查询，该查询运行良好并提供以下输出:

SELECT 
    [PropertyCode], [BkgLeadTime], COUNT([Bkg Lead Time]) AS 'BLT COUNT' 
FROM 
    BOOKINGLEADTIME_CTE
GROUP BY 
    [PropertyCode], [Bkg Lead Time]

输出:

PropertyCode     BkgLeadTime        BLT COUNT
----------------------------------------------
   ZIL               1                4
   ZIL               2                2
   ZIL               5                1
   ZIL               7                12

我需要更改上述查询，以便只得到一行结果。基本上，我想计算上面显示的输出的加权平均值。

我的新查询如下:

SELECT 
    [PropertyCode], 
    SUM([Bkg Lead Time] * COUNT([Bkg Lead  Time])) / SUM (COUNT([Bkg Lead Time])) AS 'Weighted AVG BLT'
FROM 
    BOOKINGLEADTIME_CTE
GROUP BY 
    [PropertyCode]

但是，当我运行查询时，SSMS 抛出以下错误:

Cannot perform an aggregate function on an expression containing an aggregate or a subquery.

如何修改查询以避免此错误？我知道这与我使用的聚合语法有关，但我找不到重写此查询的正确方法。

预期输出是:

PropertyCode    Weighted AVG BLT
   ZIL             5.10

Answer 1

也许这会对你有所帮助

WITH CTE_TEST
AS
(   SELECT [PropertyCode], [BkgLeadTime], COUNT([Bkg Lead Time]) AS 'BLT_COUNT' 
    FROM BOOKINGLEADTIME_CTE
    GROUP BY [PropertyCode], [Bkg Lead Time]
)
SELECT SUM([BkgLeadTime]*[BLT_COUNT]) / SUM([BLT_COUNT]) FROM CTE_TEST