Re: Inconsistent results for division and multiplication operations - Mailing list pgsql-sql

If the number of significant digits in the input is not fixed, it becomes challenging to achieve consistent results by rounding.

for example

postgres=# select round(1.003/1.002*5.01,2);

         ?column?

--------------------------

 5.01  

(1 row)

postgres=# select round(1.003*5.01/1.002,2);

      ?column?

--------------------

 5.02

(1 row)

Correct. That's why you should always use numeric with the desired precision if you want precision numbers.

for instance
select 1.003/1.002*5.01 :: numeric(10,4)
will give the same result as
select 1.003*5.01/1.002 :: numeric(10,4)

They are much slower to calculate than floating point, however, so if you don't care about precision you can keep using just floating point.

Regards,