Editing Count(CASE WHEN to sum an Aggregate Value

Question

I am using CASE WHEN in my select statement to count the number of records where a condition is true:

 COUNT(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) 
                 - CONTRACT_EFFECTIVE_DATE = 1 THEN 1 END) AS "1 day",

That works fine.

Now I am attempting to apply the same condition but to sum the values in a column where it is true, rather than counting the records. Here is what I have tried:

 (CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) 
          - CONTRACT_EFFECTIVE_DATE = 0 THEN SUM(DWELL_MINUTES) END) AS "0 day", 

But that gave error "Selected non aggregate must be part of the associated group".

I tried some more variations with no success.

How would I sum the values contained in DWELL_MINUTES when CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE = 0?

Answer 1

You need to change the aggregation function in your original query from COUNT to SUM:

SUM(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) - 
              CONTRACT_EFFECTIVE_DATE = 0 THEN DWELL_MINUTES END) AS "0 day"

Answer 2

Do it the other way round, just like with COUNT. Do the evaluation per record and aggregate the results:

SUM(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) 
     - CONTRACT_EFFECTIVE_DATE = 0 THEN DWELL_MINUTES END) AS "0 day",