In cloud you can lookup data from SQL but only from workflow or after a forms submission has already been made.
If you want to do a real time lookup on a form, you would need a copy of the data in a simple table right?
However if you wanted up-to-date data, then you would need to get a copy of the current data overnight.
But with workflow limiting activities to 10k per day, how would you do this?
Just updating the data for about 4k rows exceeds the 10k limit because the For Each Activity counts as one of the activities as well as the INSERT rule.