Why set analaysis sum ( minus ) gives different result when seperate?

[yanivvl0]

hi to all qv helpers ,

can anyone tell me why the result of the 2 expressions is not the same :

sum (    {$<Subject={1},[s_code]={3},[z_code]={1}>}   val_a - val_b   )  

sum (    {$<Subject={1},[s_code]={3},[z_code]={1}>}   val_a     ) –

sum (    {$<Subject={1},[s_code]={3},[z_code]={1}>}     val_b     )  

thanks !

[sunny_talwar]

Not really sure why it would do that, do you have a sample to show the issue?

[marcus_sommer · Accepted solution]

Your first expression will be evaluated on record-level and if for example val_a or val_b isn't numeric or NULL the result for this record will be NULL. Your second expression will subtract the aggregation from two columns. And therefore you could get different results.

- Marcus

[yanivvl0]

thanks Marcus - yea this is it.