Question

在下面的查询中，当我有两个左连接时，我遇到了麻烦。会发生什么是两个左连接的总和不正确（提升）。当我删除第二个左连接时，查询正确运行。如何使用第二个左连接运行此查询？

SELECT o.IdNoLocation,
COUNT(DISTINCT o.EncodedId) AS "Frequency", 
ISNULL(SUM(o.Subtotal), 0) AS "Spend", 
ISNULL(SUM(os.Amount), 0) AS "Surcharges",
ISNULL(SUM(od.Amount), 0) AS "Discounts" 
FROM ((tblOrder o
LEFT JOIN tblOrderSurcharge os ON o.OrderId=os.OrderId) 
LEFT JOIN tblOrderDiscount od ON o.OrderId=od.OrderId)
WHERE 
o.BusinessDate BETWEEN '2014-01-01' AND '2014-12-31'
AND o.IdNoLocation <> 'X'
GROUP BY o.IdNoLocation

Answer 1

当tblOrderSurcharge或tblOrderDiscount中有多个相关行时，这是预期的结果...您在这两个表的行之间有一个隐式的半交叉连接。

如果你需要在一个声明中返回的总数，有几种“修复”这种方法。

一种选择是使用内联视图执行总计，然后组合行。实质上，运行单独的查询以从每个表中获取总计，然后将结果组合在唯一键上。例如：

SELECT o.IdNoLocation
     , o.Frequency
     , ISNULL(o.Spend, 0)       AS Spend
     , ISNULL(s.Surcharges), 0) AS Surcharges
     , ISNULL(s.Discounts), 0)  AS Discounts
  FROM ( SELECT ooo.IdNoLocation
              , COUNT(DISTINCT ooo.EncodedId) AS Frequency
              , SUM(ooo.Subtotal) AS Spend
           FROM tblOrder ooo
          WHERE ooo.BusinessDate BETWEEN '2014-01-01' AND '2014-12-31'
            AND ooo.IdNoLocation <> 'X'
         GROUP BY ooo.IdNoLocation
       ) o
  LEFT
  JOIN ( SELECT oso.IdNoLocation
              , SUM(oss.Amount) AS Surcharges
           FROM tblOrderSurcharge oss
           JOIN tblOrder oso
             ON oso.OrderId = oss.OrderId
          WHERE oso.BusinessDate BETWEEN '2014-01-01' AND '2014-12-31'
            AND oso.IdNoLocation <> 'X'
          GROUP BY oso.IdNoLocation
       ) s
    ON s.IdNoLocation = o.IdNoLocation
  LEFT
  JOIN ( SELECT odo.IdNoLocation
              , SUM(odd.Amount) AS Discounts
           FROM tblOrderDiscount odd
           JOIN tblOrder odo
             ON odo.OrderId = odd.OrderId
          WHERE odo.BusinessDate BETWEEN '2014-01-01' AND '2014-12-31'
            AND odo.IdNoLocation <> 'X'
          GROUP BY odo.IdNoLocation
       ) d
    ON d.IdNoLocation = o.IdNoLocation

（这不经过测试，只需检查桌面。运行每个内联视图查询（o，s，d）并验证每个查询的结果是否符合预期。然后，运行整个查询，合并行...在外部查询中，我们将执行“外部”连接并处理“缺失”行并用零替换NULL）

另一种选择是在SELECT列表中使用相关子查询。

Answer 2

要了解为什么这不起作用，请运行此查询：

SELECT o.IdNoLocation,
o.EncodedId AS "Frequency", 
o.Subtotal AS "Spend", 
os.Amount AS "Surcharges",
od.Amount AS "Discounts" 
FROM ((tblOrder o
LEFT JOIN tblOrderSurcharge os ON o.OrderId=os.OrderId) 
LEFT JOIN tblOrderDiscount od ON o.OrderId=od.OrderId)
WHERE 
o.BusinessDate BETWEEN '2014-01-01' AND '2014-12-31'
AND o.IdNoLocation <> 'X'

＆＃39;正确＆＃39;答案是使用一张表来收取附加费和折扣。我认为这不再是一个选项，但你可以使用在两个表之间执行UNION ALL的视图来伪造它。

带有两个LEFT JOIN的SUM问题

2 个答案: