don't worry about being negative, its only via constructive criticism that the people at Webassist can improve things.
personally, i find dataassist to be really useful for what i would call straightforward stuff, but for more complex sql tasks, i tend to do the basic stuff in dataassist, then hand code as necessary.
This may not be good general advice, it's just an approach i tend to take.
as to your problem, are you looking to query 3 fields from a single table or from several tables ?
can you give an indication of your table(s) structure and what you want to achieve, as this can help me