我有一些客户收到了奇怪的账单。我已经成功地确定了核心问题:
SELECT 199.96 - (0.0 * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * CAST(199.96 AS DECIMAL(19, 4)))) -- 200 what the?
SELECT 199.96 - (0.0 * FLOOR(1.0 * CAST(199.96 AS DECIMAL(19, 4)))) -- 199.96
SELECT 199.96 - (0.0 * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * 199.96)) -- 199.96
SELECT 199.96 - (CAST(0.0 AS DECIMAL(19, 4)) * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * CAST(199.96 AS DECIMAL(19, 4)))) -- 199.96
SELECT 199.96 - (CAST(0.0 AS DECIMAL(19, 4)) * FLOOR(1.0 * CAST(199.96 AS DECIMAL(19, 4)))) -- 199.96
SELECT 199.96 - (CAST(0.0 AS DECIMAL(19, 4)) * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * 199.96)) -- 199.96
-- It gets weirder...
SELECT (0 * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * CAST(199.96 AS DECIMAL(19, 4)))) -- 0
SELECT (0 * FLOOR(1.0 * CAST(199.96 AS DECIMAL(19, 4)))) -- 0
SELECT (0 * FLOOR(CAST(1.0 AS DECIMAL(19, 4)) * 199.96)) -- 0
-- so... ... 199.06 - 0 equals 200... ... right???
SELECT 199.96 - 0 -- 199.96 ...NO....
有没有人知道这里到底发生了什么?我的意思是,这肯定与十进制数据类型有关,但我真的无法理解...
对于数字文字的数据类型有很多混淆,所以我决定展示实际行:
PS.SharePrice - (CAST((@InstallmentCount - 1) AS DECIMAL(19, 4)) * CAST(FLOOR(@InstallmentPercent * PS.SharePrice) AS DECIMAL(19, 4))))
PS.SharePrice DECIMAL(19, 4)
@InstallmentCount INT
@InstallmentPercent DECIMAL(19, 4)
我确保每个有一个不同于
DECIMAL(19, 4)
类型的操作数的操作结果在应用到外部上下文之前进行了显式转换。
尽管如此,结果仍然是200.00
。
我现在创建了一个精简的样例,您可以在计算机上执行。
DECLARE @InstallmentIndex INT = 1
DECLARE @InstallmentCount INT = 1
DECLARE @InstallmentPercent DECIMAL(19, 4) = 1.0
DECLARE @PS TABLE (SharePrice DECIMAL(19, 4))
INSERT INTO @PS (SharePrice) VALUES (599.96)
-- 2000
SELECT
IIF(@InstallmentIndex < @InstallmentCount,
FLOOR(@InstallmentPercent * PS.SharePrice),
1999.96)
FROM @PS PS
-- 2000
SELECT
IIF(@InstallmentIndex < @InstallmentCount,
FLOOR(@InstallmentPercent * CAST(599.96 AS DECIMAL(19, 4))),
1999.96)
FROM @PS PS
-- 1996.96
SELECT
IIF(@InstallmentIndex < @InstallmentCount,
FLOOR(@InstallmentPercent * 599.96),
1999.96)
FROM @PS PS
-- Funny enough - with this sample explicitly converting EVERYTHING to DECIMAL(19, 4) - it still doesn't work...
-- 2000
SELECT
IIF(@InstallmentIndex < @InstallmentCount,
FLOOR(@InstallmentPercent * CAST(199.96 AS DECIMAL(19, 4))),
CAST(1999.96 AS DECIMAL(19, 4)))
FROM @PS PS
现在我有一些东西…
-- 2000
SELECT
IIF(1 = 2,
FLOOR(CAST(1.0 AS decimal(19, 4)) * CAST(199.96 AS DECIMAL(19, 4))),
CAST(1999.96 AS DECIMAL(19, 4)))
-- 1999.9600
SELECT
IIF(1 = 2,
CAST(FLOOR(CAST(1.0 AS decimal(19, 4)) * CAST(199.96 AS DECIMAL(19, 4))) AS INT),
CAST(1999.96 AS DECIMAL(19, 4)))
到底是怎么回事,floor函数本来就应该返回整数,为什么会出现这种情况?:-D
我觉得我现在已经把问题精简到了最核心的部分 :-D
-- 1.96
SELECT IIF(1 = 2,
CAST(1.0 AS DECIMAL (36, 0)),
CAST(1.96 AS DECIMAL(19, 4))
)
-- 2.0
SELECT IIF(1 = 2,
CAST(1.0 AS DECIMAL (37, 0)),
CAST(1.96 AS DECIMAL(19, 4))
)
-- 2
SELECT IIF(1 = 2,
CAST(1.0 AS DECIMAL (38, 0)),
CAST(1.96 AS DECIMAL(19, 4))
)
float
类型。 - Panagiotis KanavosFloor()
不会返回一个int
。它返回与原始表达式相同的类型,但去除了小数部分。对于其余部分,IIF()
函数的结果是具有最高优先级的类型 (https://learn.microsoft.com/en-us/sql/t-sql/functions/logical-functions-iif-transact-sql)。因此,在第二个示例中,您将转换为 int,较高的优先级是简单的 numeric(19,4) 转换。 - Joel Coehoorn