Question

我的意思是，假设你有一张表：

Col1 Col2
---- ----
 1    1
 1    9
 2    1
 2    3
 4    1
 4    2

我想得到：Col1 = 4且Col2 = 2，因为Col1具有优先权。换句话说，我想要Col1的最大值，并且该值是最小T-SQL表达式中Col2的最大值。这几乎就像说：

SELECT TOP 1 Col1, Col2
FROM MyTable
ORDER BY Col1, Col2 DESC

但是这样做可以使Col1，Col2值在另一个查询中可用。

Answer 1

不像MAX(Col1, Col2)那样。如果您想模拟MAX ... GROUP BY X，可以使用

WITH T AS
(
SELECT Col1,
       Col2,
       ROW_NUMBER () OVER (PARTITION BY X ORDER BY Col1 DESC, Col2 DESC) AS RN
FROM MyTable
)
SELECT Col1,
       Col2,
          X
FROM T
WHERE RN= 1;

Answer 2

喜欢这个？一行

SELECT ...
FROM
   SOmeTable
   JOIN
   (
    SELECT TOP 1 Col1, Col2
    FROM MyTable
    ORDER BY Col1, Col2 DESC
    ) foo ON S.Col1 = foo.Col1

或者每个外排？

SELECT ...
FROM
   SOmeTable S
   CROSS APPLY
   (
    SELECT TOP 1 Col2
    FROM MyTable M
    WHERE S.somecol = M.SomeCol
    ORDER BY Col2 DESC
    ) foo

SELECT ...
FROM
   SOmeTable S
   CROSS APPLY
   (
    SELECT Col1, MAX(Col2) AS MaxCOl2
    FROM MyTable M
    GROUP BY Col1
    ) foo ON S.Col1 = foo.Col1

Answer 3

WITH t(Col1,maxCol1,maxCol2) AS (
  SELECT
    Col1,
    MAX(Col1) OVER(),
    MAX(Col2) OVER(PARTITION BY Col1)
)
SELECT TOP 1 maxCo11,maxCol2 FROM t WHERE Col1 = maxCol1

是否有用于获取两列最大值的T-SQL快捷方式

3 个答案: