sql server round函数的疑惑

sdchy

　　今天在为项目解决一个问题的时候，碰到一个很操蛋的问题。
　　关于ROUND函数，我们平常理解为4舍5入，如：
　　print ROUND(12.555, 2);
　　结果为：12.56
　　
　　另外看三段脚本：
　　1，
　　declare @Value1 float, @Digit1 int
set @Value1=12.055;
set @Digit1=2;
print '12.055 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.155;
print '12.155 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.255;
print '12.255 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.355;
print '12.355 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.455;
print '12.455 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.555;
print '12.555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.655;
print '12.655 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.755;
print '12.755 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.855;
print '12.855 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.955;
print '12.955 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
　　12.055 --> 12.05
12.155 --> 12.15
12.255 --> 12.26
12.355 --> 12.36
12.455 --> 12.46
12.555 --> 12.55
12.655 --> 12.65
12.755 --> 12.76
12.855 --> 12.86
12.955 --> 12.96
　　
　　2，
　　declare @Value1 float, @Digit1 int
set @Value1=12.0555;
set @Digit1=2;
print '12.0555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.1555;
print '12.1555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.2555;
print '12.2555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.3555;
print '12.3555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.4555;
print '12.4555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.5555;
print '12.5555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.6555;
print '12.6555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.7555;
print '12.7555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.8555;
print '12.8555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.9555;
print '12.9555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
　　12.0555 --> 12.06
12.1555 --> 12.16
12.2555 --> 12.26
12.3555 --> 12.36
12.4555 --> 12.46
12.5555 --> 12.56
12.6555 --> 12.66
12.7555 --> 12.76
12.8555 --> 12.86
12.9555 --> 12.96

　　
　　3，
　　declare @Value1 float, @Digit1 int
set @Value1=12.0555;
set @Digit1=3;
print '12.0555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.1555;
print '12.1555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.2555;
print '12.2555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.3555;
print '12.3555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.4555;
print '12.4555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.5555;
print '12.5555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.6555;
print '12.6555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.7555;
print '12.7555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.8555;
print '12.8555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
set @Value1=12.9555;
print '12.9555 --> ' + cast(ROUND(@Value1, @Digit1) as varchar);
　　12.0555 --> 12.056
12.1555 --> 12.155
12.2555 --> 12.255
12.3555 --> 12.355
12.4555 --> 12.456
12.5555 --> 12.556
12.6555 --> 12.656
12.7555 --> 12.755
12.8555 --> 12.855
12.9555 --> 12.956
　　阿斯多夫