I am trying to get the related revenue element on/from each order line. I am not getting any results with this query: select transaction.entity, transactionline.revenueelement from transaction INNER JOIN transactionline ON transaction.id=transactionline.id where transaction.id = 460691

Are you sure you have a transaction with an internal id with 460691? There isn't an error in the query. Are you getting any results if you don't include the WHERE clause? try and use one with an id that is returned

select transaction.id, transaction.entity, transactionline.revenueelement from transaction INNER JOIN transactionline ON transaction.id=transactionline.id

I think the join condition may be the problem. You should be joining on

transaction.id = transactionline.transaction

it worked! thanks @scottvonduhn