Depends on how complex the views are. Simple views that just narrow and/or filter a table, fine. Couple of joins, probably fine. Lots and lots of joins, aggregation, views upon views, you're asking for performance problems. Partially from the complexity making it harder for the optimiser to find a good plan, partially from the time required to inline all the views and simplify and partially because the optimiser may decide to materialise an interim resultset due to the aggregations, sorting, etc.