是否有获得两列

Question

的最高值的T-SQL快捷

我的意思是，说你有一个像表：

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

我想：Col1中= 4和col2的= 2，因为Col1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。这几乎像是在说：

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

但在这样一种方式，Col1中这样做，col2的值是另一个查询中使用。

Answer 1

是否这样？一排

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

还是每个外排？

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 2

其实没有什么像MAX(Col1, Col2)。如果你想模拟MAX ... GROUP BY X你可以使用

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 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