Question

This evaluation in sql doesn’t seems to work properly for some reason but i can’t figure out why.

Lets take this example first.

DECLARE @countRatio decimal(6,3)     
SET @countRatio = (((4)/(2))*(6))/100.0
_______________________________________
0,120

This evaluation works like a charm. I also get the same answer with my calculator.

But this example give me an unexpected answer.

DECLARE @countRatio decimal(6,3)     
SET @countRatio = (((2)/(4))*(6))/100.0
_______________________________________
0,000

When i calculate this on my calculator the answer is 0,03
which acording to me is correct. But the sql keeps giving me 0,000 as the answer. Any ideas?

Answer 1

The problem is that ((2)/(4)) is rounded down to an INT since 2 and 4 are both INTs. If you instead use 2.0 or 4.0 you get the right result:

DECLARE @countRatio decimal(6,3)     
SET @countRatio = (((2.0)/(4))*(6))/100.0
SELECT @countRatio 
==========================
0.030

In any arithmetic expression, SQL Server casts to the type of the operator that has the greater precision. So 2.0/4 casts the result to the type of 2.0, which is float.