Here is interesting question I received yesterday. I personally think it is one of the most interesting questions I have received this month.
“Can Database Primary File Have Any Other Extention Than MDF?”
Before you read the answer – think for a moment.
Now read the answer in the next line.
Yes, Of course. MDF file extension of the primary data file of the database is just a normal practice, but essentially, you can use any other database file extension as well.
Here is an example where I am able to attach files with PDF extension to the database. Please note that this file was created by SQL Server earlier and was always used for primary data file.
USE [master] GO CREATE DATABASE [tests] ON ( FILENAME = N'D:\data\tests.pdf' ), ( FILENAME = N'D:\data\tests_log.ldf' ) FOR ATTACH GO
As you can see that other extensions are successfully restored to the database. If you want to practice this example, you can download this example by clicking over here.
Reference: Pinal Dave (https://blog.sqlauthority.com)