Question

my SQL query which works fine is

select case month(timestamp_iso(STATUSDATE))
        when 1 then 'January'
        when 2 then 'February'
        when 3 then 'March'
        when 4 then 'April'
        when 5 then 'May'
        when 6 then 'Jun'
        when 7 then 'July'
        when 8 then 'August'
        when 9 then 'September' 
        when 10 then 'October'
        when 11 then 'November'
        when 12 then 'December'
    end as Month, 

    count (case when service='ADSL' then 1 end) as  ADSL,
  AVG (timestampdiff(
  4, 
  char(actualfinish - reportdate))/60.00) as efficiecny



from INCIDENT
where   year(STATUSDATE) = year(current_timestamp) 
group by month(timestamp_iso(STATUSDATE))

I want to get for each month number of services with ADSL (it is done through the first COUNT)
and average time difference in hours for the records which do not have service ADSL. So I must exclude in the AVG function all records with service ADSL but I can not put it in where clause

 where   year(STATUSDATE) = year(current_timestamp) and service!='ADSL' 

because my COUNT function needs to have service=’ADSL’

How to solve this?

Thanks

Answer 1

As Avg() aggregate function ignores nulls, you can set expression to null if service is ‘ADSL’. Avg() will then ignore those records.

   AVG (case when service != 'ADSL'
             then timestampdiff(4, char(actualfinish - reportdate))/60.00) 
             else null
         end) as efficiency

You could try with coalesce:

   COALESCE (AVG (case when service != 'ADSL'
             then timestampdiff(4, char(actualfinish - reportdate))/60.00) 
             else null
         end), 0) as efficiency