本文介绍了有 5 的 SQL Server 舍入问题的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
据我所知,当四舍五入数为 5 时,根据数学四舍五入应该如下工作.
As far as i know according to mathematics rounding should work as below when rounding number is 5.
2.435 => 2.44 (Round Up, if rounding to digit(3) is odd number)
2.445 => 2.44 (Round Down, if rounding to digit(4) is even number)
如果求和没问题,
2.435 + 2.445 = 4.88
2.44 + 2.44 = 4.88
我很确定在 .Net 中也有这样的舍入方式.
I'm pretty sure in .Net also rounding works like this.
但在 SQL Server 中,5 总是四舍五入,根据数学计算是不正确的.
But in SQL server, 5 is always rounding up which is not correct according to maths.
SELECT round(2.345, 2) = 2.35
SELECT round(2.335, 2) => 2.34
这导致四舍五入值的总和存在 1 美分的差异.
this results to 1 cent discrepancies in summation of rounded values.
2.345 + 2.335 = 4.68
2.35 + 2.34 = 4.69 => which is not correct
我已经尝试过使用小数和货币数据类型.
I have tried this with decimal and money data types.
我做错了吗?有没有办法解决这个问题?
Am i doing something wrong? Is there a work around for this?
推荐答案
如果您确实想在 SQL Server 中使用银行家的舍入...
If you do want to use banker's rounding in SQL Server...
CREATE FUNCTION BankersRounding(@value decimal(36,11), @significantDigits INT)
RETURNS MONEY
AS
BEGIN
-- if value = 12.345 and signficantDigits = 2...
-- base = 1000
declare @base int = power(10, @significantDigits + 1)
-- roundingValue = 12345
declare @roundingValue decimal(36,11) = floor(abs(@value) * @base)
-- roundingDigit = 5
declare @roundingDigit int = @roundingValue % 10
-- significantValue = 1234
declare @significantValue decimal(36,11) = floor(@roundingValue / 10)
-- lastSignificantDigit = 4
declare @lastSignificantDigit int = @significantValue % 10
-- awayFromZero = 12.35
declare @awayFromZero money = (@significantValue + 1) / (@base / 10)
-- towardsZero = 12.34
declare @towardsZero money = @significantValue / (@base / 10)
-- negative values handled slightly different
if @value < 0
begin
-- awayFromZero = -12.35
set @awayFromZero = ((-1 * @significantValue) - 1) / (@base / 10)
-- towardsZero = -12.34
set @towardsZero = (-1 * @significantValue) / (@base / 10)
end
-- default to towards zero (i.e. assume thousandths digit is 0-4)
declare @rv money = @towardsZero
if @roundingDigit > 5
set @rv = @awayFromZero -- 5-9 goes away from 0
else if @roundingDigit = 5
begin
-- 5 goes to nearest even number (towards zero if even, away from zero if odd)
set @rv = case when @lastSignificantDigit % 2 = 0 then @towardsZero else @awayFromZero end
end
return @rv
end
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