SQL Group BY SUM一列並選擇第一行的分組項

Question

我有一個零件表，我有5個字段。 我想要顯示mfgpn的QTY，同時顯示其他3個字段的第一個返回行（Manfucturer，DateCode，Description）。 我最初想到如下使用MIN函數，但這並不能真正幫助我，因為數據不是int數據類型。 我該怎么做呢？ 現在我堅持下面的查詢：

SELECT SUM([QTY]) AS QTY
  ,[MFGPN]
  ,MIN([MANUFACTURER]) AS MANUFACTURER
  ,MIN([DATECODE]) AS DateCode
  ,MIN([DESCRIPTION]) AS DESCRIPTION
  INTO part
GROUP BY MFGPN, MANUFACTURER, DATECODE, description
ORDER BY mfgpn ASC

Answer 1

CROSS APPLY會為你工作嗎？

SELECT 
    SUM(a.[QTY]) AS QTY
    ,a.[MFGPN]
    ,c.[MANUFACTURER]
    ,c.[DATECODE]
    ,c.[DESCRIPTION]
FROM part a
    CROSS APPLY (SELECT TOP 1 * FROM part b WHERE a.[MFGPN] = b.[MFGPN]) c
GROUP BY 
    a.[MFGPN]
    ,c.[MANUFACTURER]
    ,c.[DATECODE]
    ,c.[DESCRIPTION]

---

測試如下：

DECLARE @T1 AS TABLE (
    [QTY] int
    ,[MFGPN] NVARCHAR(50)
    ,[MANUFACTURER] NVARCHAR(50)
    ,[DATECODE] DATE
    ,[DESCRIPTION] NVARCHAR(50));

INSERT @T1 VALUES
(2, 'MFGPN-1', 'MANUFACTURER-A', '20120101', 'A-1'),
(4, 'MFGPN-1', 'MANUFACTURER-B', '20120102', 'B-1'),
(3, 'MFGPN-1', 'MANUFACTURER-C', '20120103', 'C-1'),
(1, 'MFGPN-2', 'MANUFACTURER-A', '20120101', 'A-2'),
(5, 'MFGPN-2', 'MANUFACTURER-B', '20120101', 'B-2')

SELECT 
    SUM(a.[QTY]) AS QTY
    ,a.[MFGPN]
    ,c.[MANUFACTURER]
    ,c.[DATECODE]
    ,c.[DESCRIPTION]
FROM @T1 a
    CROSS APPLY (SELECT TOP 1 * FROM @T1 b WHERE a.[MFGPN] = b.[MFGPN]) c
GROUP BY 
    a.[MFGPN]
    ,c.[MANUFACTURER]
    ,c.[DATECODE]
    ,c.[DESCRIPTION]

產生

QTY MFGPN   MANUFACTURER    DATECODE    DESCRIPTION
9   MFGPN-1 MANUFACTURER-A  2012-01-01  A-1
6   MFGPN-2 MANUFACTURER-A  2012-01-01  A-2

Answer 2

這可以通過窗口 SUM()輕松管理：

WITH summed_and_ranked AS (
  SELECT
    MFGPN,
    MANUFACTURER,
    DATECODE,
    DESCRIPTION,
    QTY = SUM(QTY) OVER (PARTITION BY MFGPN),
    RNK = ROW_NUMBER() OVER (
      PARTITION BY MFGPN
      ORDER BY DATECODE  -- or which column should define the order?
    )
  FROM atable
)
SELECT
  MFGPN,
  MANUFACTURER,
  DATECODE,
  DESCRIPTION,
  QTY,
INTO parts
FROM summed_and_ranked
WHERE RNK = 1
;

對於每一行，計算組中的總組數量和排名。 當實際獲取用於插入新表（主SELECT）的行時，僅拉取RNK值為1的行。 因此，您將獲得包含組總計的結果集以及某些行的詳細信息。