Re: PostgreSQL needs percentage function

[Edson Carlos Ericksson Richter <richter@xxxxxxxxxxxxxx>]

Em 18/12/2017 14:28, Michael Nolan escreveu:

On Mon, Dec 18, 2017 at 6:23 AM, Nick Dro <postgresql@xxxxxxxxxxx> wrote:

Hi,

Why PostgreSQL doesn't have build-in function to calculate percentage? somthing like percent(number,%

for example:

select percent(100,1) will calculate 1% of 100 = 1

select percent(25,20) will calculate 20% of 25 = 5

 

Seems like a nice addition to the math functions list:

https://www.postgresql.org/docs/9.5/static/functions-math.html

 

This is veryhelpull function, many uses percentage calculation in thier work and it will simplify the process. Percentage calculation is considered a basic math operation and I think postgresql should support it as a build-in function.

Seems like easy to implment isn't it?

It's a bit trickier than that, because you';ll have to deal with integers, real, double precision, etc.  You may also want to deal with null values.  I found it more useful to write a function that displays X as a percentage of Y, rounded to 1 digit to the right of the decimal point.

--

Mike Nolan

I believe that having a built-in function for percentage is not a good idea. Is just like having a function to calculate fractions... Someone would like to have percentages as 0..1, others would like to have it multiplied by 100. How to deal with integers? And so on (as others already stated here).

But, is it possible to have a aggregate function that calculates de percent from the sum (and/or count) total (as a value from 0 ... 1) for numeric (or double)?

Looking really superficially seems to me that would be a great addition to the aggreggates (and is not just a trivial div/multiply op)


Edson