Query giving division by zero error in PostgreSQL

Question

I am trying to run the following query which results me postgres error: division by zero

select 
    request_count,
    response_count, 
    (response_count*100) / (request_count+response_count) AS proportion 
from total_dummy_table; 

How can I avoid and resolve the division by zero error?

Tried to fix using the below query but getting the same result as above

SELECT 
    request_count,
    response_count,
    (response_count*100) / (request_count) AS proportion 
FROM 
    total_dummy_table
ORDER BY 
    (response_count*100) /(CASE request_count WHEN 0 Then NULL ELSE request_count END) DESC NULLS FIRST

Please let me know where am I doing wrong, or how can I fix this. Thanks!

Result expectation:

The query should return me something like below:

Request_count | Response_count | Proportion

1603423       |  585706        | 36.52

Quick note: Table total_dummy_table does not have column name proportion that is the addition to the result which have calculated proportion in it.

Solution 1

select request_count,response_count, 
case 
    when 
    request_count+response_count = 0 then 0 
    else
(response_count*100) / (request_count+response_count) 
end AS proportion 
from total_dummy_table;

Solution 2

use NULLIF

something/NULLIF(column_name,0)

NULLIF(col,val) is shorthand for

CASE WHEN col=val THEN NULL ELSE col

Comments

[AKIWEB]

Thank you Hourari, quick question and very dumb too- here the total count according to me is request_count, out of which how many people responded is a response_count. So my understanding says the total have to be just request_count not the addition of them? correct? I am just curious.

[Houari]

It depends of what do you want to calculate/display. My answer was to avoid the divison by zero error :)

[Rahul]

This should be accepted as the right answer. Its tedious to repeat the denominator. Especially if its a big expression, you will the feel the pain repeating the whole denominator as in @Houari 's answer

[AsAP_Sherb]

I agree, this is the more succinct solution. coding a case statement is unnecessary, and the real answer is Null not 0.

[AsAP_Sherb]

NULLIF is a more appropriate solution to avoid divide by zero errors, and is also a much more simple solution. I recommend the answer from diego

[Jar]

nullIf is better