Math.Round and SQL Server Round

[Guest]

I'm trying to determine the best approach for rounding in an application I'm
building. Unfortunately it appears as though SQL Server and VB.NET round in
different ways.

SQL Server

select round(123.465,2)

returns

123.470

Which I think is correct.

VB.NET

Math.Round(123.465, 2)

returns

123.46

Through online help I have read that the VB.NET way of doing it is "called
rounding to nearest, or banker's rounding."

I guess my first question is what is correct (when determining Tax or Sale
prices)?

My next question is what is the best approach for standarizing? Can I make
SQL Server act like VB.NET or VB.NET act like SQL Server?

Are there additional functions either in SQL Server or VB.NET that I am
missing?

Also it appears as if the behavior is consistent throughout the VB.NET
environment (formatcurrency and formatpercent).

There are certain parts of the applicaiton where it makes sense for SQL
Server to calculate some of the numbers and other where it makes sense for
VB.NET to.

Thanks

 

[David Gugick]

I guess my first question is what is correct (when determining Tax or
Sale prices)?

Your accountant / CFO should be able to tell you which is the correct
accounting method. Why is this calculation being left to the
programmers? This is a financial matter, not a programming one.

 

[Guest]

I realize this is an accountant question, but if I'm playing every role, it's
now my decision. I can't imagine that this type of question is not addressed
with almost every ecommerce site on the Internet. Once a decision is made, I
will need to know how to implement the appropriate functionality either on
SQL Server or insided VB.NET.

Thanks

 

[James Goodwin]

I'm trying to determine the best approach for rounding in an application I'm
building. Unfortunately it appears as though SQL Server and VB.NET round in
different ways.

SQL Server
select round(123.465,2)
returns
123.470

Which I think is correct.

VB.NET
Math.Round(123.465, 2)
returns
123.46

VB Rounds a 5 to the nearest EVEN number so:
123.465 becomes 123.46 while 123.475 becomes 123.48 I personally consider
this to be an incredibly inconsistent form of rounding and find that is
causes numerous issues when programming. As far as I know only Microsoft
rounds this way and it might only be VB.

To Cause VB to round in a normal way take the int of +.5 so for the numbers
above Int((Num*100)+.5))/100 Or if the Floor function takes an argument for
the number of decimals Floor(Num+.005,2) I don't use VB much so I'm not
sure about the Function Names.

To Make SQL round the VB way is trickier, you need to determine whether the
rounding digit(s) = 5 and then if the digit before the rounding digit is
even or odd. Something like:

DECLARE @Num as Numeric(8,4)
Declare @Dig as Numeric(8,4)
Declare @Dig2 as Integer
Declare @Even as integer

SET @Num = 123.465
SET @Dig = @Num * 1000 - (CAST(@Num*100 as integer)*10)
SET @Dig2 = CAST(@Num * 100 as Integer) - (CAST(@Num * 10 as Integer)*10)
SET @Even = Case When @Dig2 in (2,4,6,8,0) then 1 else 0 end

SELECT Round(Case @Dig When 5 THEN CASE @Even When 1 THEN @Num-0.001

ELSE @Num+.001 END
ELSE @Num END,2)


Regards,
Jim

 

[David Gugick]

I realize this is an accountant question, but if I'm playing every
role, it's now my decision. I can't imagine that this type of
question is not addressed with almost every ecommerce site on the
Internet. Once a decision is made, I will need to know how to
implement the appropriate functionality either on SQL Server or
insided VB.NET.

Thanks

My point is if you are in charge, you should not take the word of anyone
but an accountant or someone else who is in the know. The fact that SQL
Server and VB round differently is not really an issue until you know
how you must process the data using certified accounting principles.

 

[Steve Kass]

VB Rounds a 5 to the nearest EVEN number so:
123.465 becomes 123.46 while 123.475 becomes 123.48 I personally consider
this to be an incredibly inconsistent form of rounding and find that is
causes numerous issues when programming. As far as I know only Microsoft
rounds this way and it might only be VB.

James,

This is called "Banker's Rounding", and is widely used in finance
(http://support.microsoft.com/kb/196652). It may be required by law in
some places. There is no "correct" way to round the last digit away
when a number ends in 5.

Steve Kass
Drew University