Plain and simple, does anybody know why this:
Select 30 * 220 / 30
Returns 220, which is the correct result, and this:
Select 30 * (220/30)
Returns 210???
On the second case, I realise that 220/30 is being calculated first, generating a decimal (7,333333...) but still... isn't this lousy precision?
Under integer division 220/30 = 7 and 99/100 = 0 (note truncation not rounding)
Use non integers to avoid this. e.g. Select 30 * (220/30.0)
Or you can use an explicit cast
Select 30 * (220/cast (30 as float))
The one in the parentheses, is always evaluated first, but since the machine logic you are using integer, in that case, the result of the division is 7, wich you multiply by 30, gives you 210
来源：https://stackoverflow.com/questions/4672420/sql-server-2000-integer-truncating