引入第三个表作为左连接重复值

Question

如何设置此左连接，使其不会重复我在 Table2 中的调用或在 Table3 中的销售？

左加入表 2 或表 3 返回准确的答案，左加入同一查询重复 - 虽然我有 3 个电话和 444 美元的销售额，但它返回 6 个电话（表 2 的三个记录 x 表 3 的两个记录) 和 1332 美元的销售额。

使用 SQL Server Studio 17。

CREATE TABLE #Table1 (
    CommercialTime datetime,
    NextCommercialTime datetime,
    Station varchar(4),
    Cost int    )
INSERT INTO #Table1 (
    CommercialTime,
    NextCommercialTime,
    Station,
    Cost    )
VALUES
(   '2020-04-06 12:01:00.000',
    '2020-04-06 12:15:00.000',
    'ZZZZ',
    '9999'  )

CREATE TABLE #Table2 (
    CallTime datetime,
    Station varchar(4),
    CallCount int   )
INSERT INTO #Table2 (
    CallTime,
    Station,
    CallCount   )
VALUES
(   '2020-04-06 12:02:00.000',
    'ZZZZ',
    '1' ),
(   '2020-04-06 12:05:00.000',
    'ZZZZ',
    '1' ),
(   '2020-04-06 12:07:00.000',
    'ZZZZ',
    '1' )

CREATE TABLE #Table3 (
    SaleTime datetime,
    Station varchar(4),
    SaleAmount int  )
INSERT INTO #Table3 (
    SaleTime,
    Station,
    SaleAmount  )
VALUES
(   '2020-04-06 12:04:00.000',
    'ZZZZ',
    '123'   ),
(   '2020-04-06 12:07:00.000',
    'ZZZZ',
    '321'   )

SELECT 
          one.Station
        , SUM(two.Callcount) as Calls
        , SUM(three.SaleAmount) as Sales
    FROM #Table1 one WITH(NOLOCK)
    LEFT JOIN #Table2 two   WITH(NOLOCK)    ON one.Station = two.Station 
                                                AND two.CallTime between one.CommercialTime and one.NextCommercialTime      
    LEFT JOIN #Table3 three WITH(NOLOCK)    ON one.Station = three.Station 
                                                AND three.SaleTime between one.CommercialTime and one.NextCommercialTime    
    GROUP BY one.Station

--Output:
    Station Calls   Sales
    ZZZZ    6   1332

Answer 1

对于这个问题，我建议使用子查询而不是连接，例如

SELECT 
  one.Station
  , (
    select sum(CallCount)
    from #Table2 two
    where one.Station = two.Station 
    AND two.CallTime between one.CommercialTime and one.NextCommercialTime
  ) Calls
  , (
    select sum(SaleAmount)
    from #Table3 three
    where one.Station = three.Station 
    AND three.SaleTime between one.CommercialTime and one.NextCommercialTime
  ) Sales
FROM #Table1 one

原因是连接为您提供了您不想要的所有行组合。解释一下，当您将 Table2 加入 Table1 时，您会得到 3 行：

Station TwoCallTime
ZZZZ    2020-04-06 12:02:00.000
ZZZZ    2020-04-06 12:05:00.000
ZZZZ    2020-04-06 12:07:00.000

那么当你加入有 2 行的 Table3 时，你现在有 6 行：

Station TwoCallTime             ThreeCallTime
ZZZZ    2020-04-06 12:02:00.000 2020-04-06 12:04:00.000
ZZZZ    2020-04-06 12:02:00.000 2020-04-06 12:07:00.000
ZZZZ    2020-04-06 12:05:00.000 2020-04-06 12:04:00.000
ZZZZ    2020-04-06 12:05:00.000 2020-04-06 12:07:00.000
ZZZZ    2020-04-06 12:07:00.000 2020-04-06 12:04:00.000
ZZZZ    2020-04-06 12:07:00.000 2020-04-06 12:07:00.000

这不是您在这里想要完成的。

Answer 2

您可以使用outer apply：

SELECT one.Station, ISNULL(t2.calls, 0) AS Calls, ISNULL(t3.sales, 0) AS Sales
FROM #Table1 one WITH(NOLOCK) OUTER APPLY
     ( SELECT SUM(two.Callcount) as calls
       FROM #Table2 two
       WHERE one.Station = two.Station AND 
             two.CallTime between one.CommercialTime and one.NextCommercialTime      
     ) t2 OUTER APPLY
     ( SELECT SUM(three.SaleAmount) as sales
        FROM #Table3 three
        WHERE one.Station = three.Station AND 
              three.SaleTime between one.CommercialTime and one.NextCommercialTime    
     ) t3;