This really, really depends on the database, the query, the size of the table, the indices on the involved tables, the existing load of the machine and the database in question, and the hardware and network configuration of the database server and client. You haven't provided any of that, so it's hard to give you a meaningful estimate. For a rough estimate, I would set up a secondary machine, restore a backup of the database on it and run some benchmarks or contact the presales consultants of some of the database vendors.