從多列中選擇MAX和MIN

Question

我可以從同一個表的多個列中獲得MAX()和MIN() ：

Select
    max(Maximo) as Maximo,
    min(Minimo) as Minimo
From(
    SELECT
        MAX(COLUMN1) AS Maximo,
        MIN(COLUMN2) AS Minimo
    FROM TABLE1
    WHERE
        COND1= 'A' and
        COND2= 'X'
    UNION
    SELECT
        MAX(COLUMN3) AS Maximo,
        MIN(COLUMN4) AS Minimo
    FROM TABLE1
    WHERE
        COND1= 'A' and
        COND2= 'X'
    UNION
    SELECT
        MAX(COLUMN5) AS Maximo,
        MIN(COLUMN6) AS Minimo
    FROM TABLE1
    WHERE
        COND1= 'A' and
        COND2= 'X'
    UNION
    SELECT
        MAX(COLUMN7) AS Maximo,
        MIN(COLUMN8) AS Minimo
    FROM TABLE1
    WHERE
        COND1= 'A' and
        COND2= 'X'
) x

但這看起來很丑。 所以我正在嘗試使用UNPIVOT ：

SELECT
    MIN (v) AS MinValue,
    MAX (v) AS MaxValue
FROM
    TABLE1 UNPIVOT (
        v FOR nValue IN (
            COLUMN1,
            COLUMN2,
            COLUMN3,
            COLUMN4,
            COLUMN5,
            COLUMN6,
            COLUMN7,
            COLUMN8
        )
    ) AS U

我收到以下錯誤：

[Err] 42000 - [SQL Server]Incorrect syntax near the keyword 'FOR'.

應該是什么？ 謝謝。

Answer 1

似乎您可以使用CROSS APPLY和VALUES輕松編寫此代碼，以獲得最終結果：

SELECT Maximo = max(maxVal), 
  Minimo = min(minVal)
FROM table1 t
CROSS APPLY
(
  VALUES
    (COLUMN1, COLUMN2),
    (COLUMN3, COLUMN4),
    (COLUMN5, COLUMN6),
    (COLUMN7, COLUMN8)
) c (maxVal, minVal)
WHERE t.COND1= 'A'
  AND t.COND2= 'X';

請參閱帶有演示的SQL Fiddle 。 這樣便取消了成對的列，然后您就可以獲取每列的max / min 。