GROUP BY & SUM 缺失 MONTHS 的值

Question

我已经浏览了很多示例，并加入了其中的几个，以便得出以下陈述；

DECLARE @StartDate SMALLDATETIME, @EndDate SMALLDATETIME;

SELECT @StartDate = '20170930', @EndDate = '20180930';

;WITH d(d) AS 
(
  SELECT DATEADD(MONTH, n, DATEADD(MONTH, DATEDIFF(MONTH, 0, @StartDate), 0))
  FROM ( SELECT TOP (DATEDIFF(MONTH, @StartDate, @EndDate) + 1) 
    n = ROW_NUMBER() OVER (ORDER BY [object_id]) - 1
    FROM sys.all_objects ORDER BY [object_id] ) AS n
)

SELECT 
  [Period]    = CONVERT(VARCHAR(4), YEAR(d.d)) + '-' + CONVERT(VARCHAR(2), MONTH(d.d)),
  QtyTotal = ISNULL(SUM(o.QEXIT),0)
FROM d LEFT OUTER JOIN VE_STOCKTRANS AS o
  ON o.TRANSDATE >= d.d

  AND o.TRANSDATE < DATEADD(MONTH, 1, d.d)
 WHERE STOCKID = 6000 AND TRANSTYPE = 3553
GROUP BY d.d
ORDER BY d.d;

我需要获取某件商品在过去一年的总销售量。如果该商品在该特定月份没有任何销售额，则该月份旁边应显示 0。除非提供了 WHERE 子句，否则上述查询会执行所需的操作。一旦我添加 WHERE 子句来获取特定产品的数据，没有销售的月份就会消失。

如果有经验的 SQL 开发人员能告诉我正确的方向，我将不胜感激。

谢谢

Answer 1

您需要将条件移至ON:

-- ...
SELECT 
  [Period] = CONVERT(VARCHAR(4),YEAR(d.d)) +'-'+ CONVERT(VARCHAR(2), MONTH(d.d)),
  QtyTotal = ISNULL(SUM(o.QEXIT),0)
FROM d LEFT OUTER JOIN VE_STOCKTRANS AS o
  ON o.TRANSDATE >= d.d

  AND o.TRANSDATE < DATEADD(MONTH, 1, d.d)
  AND STOCKID = 6000 AND TRANSTYPE = 3553   -- here
GROUP BY d.d
ORDER BY d.d;

Answer 2

更通用的方法是在加入之前应用过滤器。

;WITH d(d) AS 
(
  SELECT DATEADD(MONTH, n, DATEADD(MONTH, DATEDIFF(MONTH, 0, @StartDate), 0))
  FROM ( SELECT TOP (DATEDIFF(MONTH, @StartDate, @EndDate) + 1) 
    n = ROW_NUMBER() OVER (ORDER BY [object_id]) - 1
    FROM sys.all_objects ORDER BY [object_id] ) AS n
),
  o AS
(
  SELECT *
    FROM VE_STOCKTRANS
   WHERE STOCKID = 6000
     AND TRANSTYPE = 3553
)
SELECT 
  [Period] = CONVERT(VARCHAR(4), YEAR(d.d)) + '-' + CONVERT(VARCHAR(2), MONTH(d.d)),
  QtyTotal = ISNULL(SUM(o.QEXIT),0)
FROM
  d
LEFT OUTER JOIN
  o
    ON  o.TRANSDATE >= d.d
    AND o.TRANSDATE < DATEADD(MONTH, 1, d.d)
GROUP BY
  d.d
ORDER BY
  d.d;

正如您在其他答案中看到的那样，这里并不是绝对必要的。但是，在执行 FULL OUTER JOIN 或其他复杂查询时，在一个范围内过滤您的源并加入另一个范围内会非常有帮助。

（我总是过滤我的消息来源，我讨厌结块的番茄酱。）