Avoiding a divide by zero error in a case statement - sql

Question

I am getting a divide by zero error in my script.
Can anyone please help.
I am trying to divide two records and one of them has zero in it. I dont want to lose the row, please advise.
select DATEPART(Year,Request_date) as "Year",
DATEPART(Month,Request_date) as "Month",
COUNT([MONTH_OF_SUSPENSION]) as "Request" ,
sum(case when [PAYMENT_<=24HRS] = 'Y' then 1 else 0 end) as "Paid in 24hrs",
COUNT([MONTH_OF_SUSPENSION])/sum(case when [PAYMENT_<=24HRS] = 'Y' then 1 else 0 end) as "Achieved"
FROM suspension_br
where REQUEST_STATUS = 'OTHERS'
GROUP BY DATEPART(Year,Request_date),DATEPART(Month,Request_date)

Answer 1

You can introduce a second case to check the result of the sum:
case
when sum(case when [PAYMENT_<=24HRS] = 'Y' then 1 else 0 end) > 0
then COUNT([MONTH_OF_SUSPENSION])/sum(case when [PAYMENT_<=24HRS] = 'Y' then 1 else 0 end)
else 0 /* a default value that makes sense to you */
end as "Achieved"

Answer 2

Looking at your code I could assume you are using MSSQL and therefore you could use nullif which returns null if two arguments are equal. So for example your code could look like :
COUNT([MONTH_OF_SUSPENSION])/nullif(sum(case when [PAYMENT_<=24HRS] = 'Y' then 1 else 0 end),0) as "Achieved"
What it does is if the value of the sum operator is equal 0 then the divisor is turn from zero into null and that will result in the entire equation to become null.

Answer 3

use another case statement to check the result of your sum
select DATEPART(Year,Request_date) as "Year",
DATEPART(Month,Request_date) as "Month",
COUNT([MONTH_OF_SUSPENSION]) as "Request" ,
sum(case
when [PAYMENT_<=24HRS] = 'Y' then 1
else 0
end) as "Paid in 24hrs",
case
when sum(case
when [PAYMENT_<=24HRS] = 'Y' then 1
else 0
end) = 0 then 'whatever you want in this case'
else COUNT([MONTH_OF_SUSPENSION])/sum(case
when [PAYMENT_<=24HRS] = 'Y' then 1
else 0
end) as "Achieved"
FROM suspension_br
where REQUEST_STATUS = 'OTHERS'
GROUP BY DATEPART(Year,Request_date),DATEPART(Month,Request_date)
although this is pretty nasty looking, so you could tidy it up a bit with a sub-select:
select
year,
month,
request,
PaidIn24hrs,
case
when PaidIn24hrs = 0 then 'whatever you want in this case'
else request/PaidIn24hrs
end as "Achieved"
from
(
select DATEPART(Year,Request_date) as "Year",
DATEPART(Month,Request_date) as "Month",
COUNT([MONTH_OF_SUSPENSION]) as "Request" ,
sum(case
when [PAYMENT_<=24HRS] = 'Y' then 1
else 0
end) as "PaidIn24hrs"
FROM suspension_br
where REQUEST_STATUS = 'OTHERS'
GROUP BY DATEPART(Year,Request_date),DATEPART(Month,Request_date)
)