Do you know the difference between .mdf, .ndf and .ldf files?

This is a typical exam or interview questions e.g.A SQL Server file with a .mdf extension is the following (tick all options):Primary data fileSecondary data fileDatabase log file The answer could be all of them or none of them! SQL Server does not enforce file names, so you can name the database files to be anything you want with whatever extension that your fancy i.e.USE [master] GOCREATE