Aggregator Error

[MerinaPremaj]

I have a parallel job with transformer and aggregator.
while executing the job,im getting the following error in aggregator.
"No derivation found for column 'poc_id' " but i mapped all the columns from transformer to aggregator.i checked all the derivations but i could not fix it. why is it so?

Thanks.

[chulett]

What 'derivation' do you have for the POC_ID column in the aggregator? In other words, what did you tell the aggregator to do with the field - group by it? Sum it?