SQL - 分组到单独的列答案

【问题标题】：SQL - Group By Into Separate ColumnsSQL - 分组到单独的列
【发布时间】：2013-05-01 23:37:59
【问题描述】：

使用 SQL Server 2008 R2。我不确定这是否可行，但我想按两列分组，并将它们的差异放入新列中。用一个例子可能更容易解释：

前：： [日期] [ID] [AMT] [类型] 2013-01-11 36374DCD-47FE-48D8-8E70-8D3B37385311 2 20 2013-01-11 36374DCD-47FE-48D8-8E70-8D3B37385311 10 21 2013-01-11 4434E2D5-1D08-45FA-AADF-F653BF9A0D97 4 20 2013-01-11 4434E2D5-1D08-45FA-AADF-F653BF9A0D97 4 21 后：： [日期] [ID] [AMT 20] [AMT 21] 2013-01-11 36374DCD-47FE-48D8-8E70-8D3B37385311 2 10 2013-01-11 4434E2D5-1D08-45FA-AADF-F653BF9A0D97 4 4

这是我目前的 SQL：

SELECT 
    CAST(TransDate AS DATE) AS [TransDate],ItemID,COUNT(TransactionTypeID) AS [TransAmt], TransactionTypeID
FROM 
    Transactions
WHERE 
    TransDate BETWEEN '2013-01-01 10:00:00' AND '2013-02-01 10:00:00'
    AND TransactionTypeID IN (20,21)
GROUP BY
    CAST(TransDate AS DATE),ItemID,TransactionTypeID

感谢任何帮助，谢谢！

【问题讨论】：

看起来您正在尝试pivot 结果。 msdn.microsoft.com/en-us/library/ms177410(v=sql.105).aspx

标签： sql sql-server sql-server-2008 group-by

【解决方案1】：

您可以使用带有 CASE 的聚合函数将行转换为列：

SELECT CAST(TransDate AS DATE) AS [TransDate],
  ItemID,
  count(case when TransactionTypeID=20 then TransactionTypeID end) Amt_20,
  count(case when TransactionTypeID=21 then TransactionTypeID end) Amt_21
FROM Transactions
WHERE 
    TransDate BETWEEN '2013-01-01 10:00:00' AND '2013-02-01 10:00:00'
    AND TransactionTypeID IN (20,21)
GROUP BY CAST(TransDate AS DATE),ItemID;

由于您使用的是 SQL Server，因此也可以使用 PIVOT 函数编写：

select TransDate,
  ItemId,
  [20] as Amt_20,
  [21] as Amt_21
FROM
(
  SELECT CAST(TransDate AS DATE) AS [TransDate],
    ItemID,
    TransactionTypeID
  FROM Transactions
  WHERE TransDate BETWEEN '2013-01-01 10:00:00' AND '2013-02-01 10:00:00'
    AND TransactionTypeID IN (20,21)
) d
pivot
(
  count(TransactionTypeID)
  for TransactionTypeID in ([20], [21])
) piv

【讨论】：

从来不知道 Pivot 功能。效果很好，谢谢！

【解决方案2】：

bluefeet answer 可能是最好的方法，但如果您的查询变得更复杂，您可以随时使用尽可能多的 UNIONS :)

    SELECT 
        CAST(TransDate AS DATE) AS [TransDate],ItemID,COUNT(TransactionTypeID) AS [TransAmt], TransactionTypeID
    FROM 
        Transactions
    WHERE 
        TransDate BETWEEN '2013-01-01 10:00:00' AND '2013-02-01 10:00:00'
        AND TransactionTypeID IN (20)
    GROUP BY
        CAST(TransDate AS DATE),ItemID,TransactionTypeID
UNION
SELECT 
    CAST(TransDate AS DATE) AS [TransDate],ItemID,COUNT(TransactionTypeID) AS [TransAmt], TransactionTypeID
FROM 
    Transactions
WHERE 
    TransDate BETWEEN '2013-01-01 10:00:00' AND '2013-02-01 10:00:00'
    AND TransactionTypeID IN (21)
GROUP BY
    CAST(TransDate AS DATE),ItemID,TransactionTypeID

【讨论】：