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
对于SQL Server 2012:
SELECT
o.OrderId,
IIF( o.NegotiatedPrice >= o.SuggestedPrice,
o.NegotiatedPrice,
ISNULL(o.SuggestedPrice, o.NegiatedPrice)
)
FROM
Order o
其他回答
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
对于SQL Server 2012:
SELECT
o.OrderId,
IIF( o.NegotiatedPrice >= o.SuggestedPrice,
o.NegotiatedPrice,
ISNULL(o.SuggestedPrice, o.NegiatedPrice)
)
FROM
Order o
-- 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;
其他答案都很好，但如果你不得不担心有NULL值，你可能会想要这个变体:
SELECT o.OrderId,
CASE WHEN ISNULL(o.NegotiatedPrice, o.SuggestedPrice) > ISNULL(o.SuggestedPrice, o.NegotiatedPrice)
THEN ISNULL(o.NegotiatedPrice, o.SuggestedPrice)
ELSE ISNULL(o.SuggestedPrice, o.NegotiatedPrice)
END
FROM Order o
在MemSQL中执行以下操作:
-- DROP FUNCTION IF EXISTS InlineMax;
DELIMITER //
CREATE FUNCTION InlineMax(val1 INT, val2 INT) RETURNS INT AS
DECLARE
val3 INT = 0;
BEGIN
IF val1 > val2 THEN
RETURN val1;
ELSE
RETURN val2;
END IF;
END //
DELIMITER ;
SELECT InlineMax(1,2) as test;
