我想写一个这样的查询:
SELECT o.OrderId, MAX(o.NegotiatedPrice, o.SuggestedPrice)
FROM Order o
但这不是MAX函数的工作原理,对吧?它是一个聚合函数,因此它需要一个参数,然后返回所有行的MAX。
有人知道我的方法吗?
我想写一个这样的查询:
SELECT o.OrderId, MAX(o.NegotiatedPrice, o.SuggestedPrice)
FROM Order o
但这不是MAX函数的工作原理,对吧?它是一个聚合函数,因此它需要一个参数,然后返回所有行的MAX。
有人知道我的方法吗?
当前回答
子查询可以从Outer查询访问列,因此可以使用这种方法跨列使用MAX等聚合。(不过,当涉及到大量列时可能更有用)
;WITH [Order] AS
(
SELECT 1 AS OrderId, 100 AS NegotiatedPrice, 110 AS SuggestedPrice UNION ALL
SELECT 2 AS OrderId, 1000 AS NegotiatedPrice, 50 AS SuggestedPrice
)
SELECT
o.OrderId,
(SELECT MAX(price)FROM
(SELECT o.NegotiatedPrice AS price
UNION ALL SELECT o.SuggestedPrice) d)
AS MaxPrice
FROM [Order] o
其他回答
-- Simple way without "functions" or "IF" or "CASE"
-- Query to select maximum value
SELECT o.OrderId
,(SELECT MAX(v)
FROM (VALUES (o.NegotiatedPrice), (o.SuggestedPrice)) AS value(v)) AS MaxValue
FROM Order o;
其实很简单:
CREATE FUNCTION InlineMax
(
@p1 sql_variant,
@p2 sql_variant
) RETURNS sql_variant
AS
BEGIN
RETURN CASE
WHEN @p1 IS NULL AND @p2 IS NOT NULL THEN @p2
WHEN @p2 IS NULL AND @p1 IS NOT NULL THEN @p1
WHEN @p1 > @p2 THEN @p1
ELSE @p2 END
END;
试试这个。它可以处理2个以上的值
SELECT Max(v) FROM (VALUES (1), (2), (3)) AS value(v)
最简单的形式是……
CREATE FUNCTION fnGreatestInt (@Int1 int, @Int2 int )
RETURNS int
AS
BEGIN
IF @Int1 >= ISNULL(@Int2,@Int1)
RETURN @Int1
ELSE
RETURN @Int2
RETURN NULL --Never Hit
END
子查询可以从Outer查询访问列,因此可以使用这种方法跨列使用MAX等聚合。(不过,当涉及到大量列时可能更有用)
;WITH [Order] AS
(
SELECT 1 AS OrderId, 100 AS NegotiatedPrice, 110 AS SuggestedPrice UNION ALL
SELECT 2 AS OrderId, 1000 AS NegotiatedPrice, 50 AS SuggestedPrice
)
SELECT
o.OrderId,
(SELECT MAX(price)FROM
(SELECT o.NegotiatedPrice AS price
UNION ALL SELECT o.SuggestedPrice) d)
AS MaxPrice
FROM [Order] o