Sum of columns in datagrid via association

I have a datagrid with source as association. I need to calculate sum for some of the columns, however when i select the aggregate option for sum, it says data source should be xpath. Can this not be achieved without xpath in datagrid? If yes, how can i retrieve association with xpath?
1 answers

If you’re not building a mobile app, if not then select xpath as datasource and select the path in the entity select dialog so that you have the same entity via association as you have in the database datasource option.