Need information regarding file renaming

No. Conceptually, there is no such thing as "file name extension". (From your question, it's not obvious that you mean exactly that though, so I'm just guessing.) Historically, old file systems and OS has such notion, but later on it was deprecated, and there is just a file name, not subdivided into any required parts. Still, traditionally, some end part of a file name is used to indicate the "file type".

In Windows, some of such "extensions" are registered to tell the Shell which default program it use to handle the file. However, the naming schema can be anything, it is note required to carry any significant information. In general case, by looking just at the file name, it's impossible to say what's inside, even in Windows (example is "*.mpg", "*.mp4": you can guess that this is a media type, but you don't know almost anything about its format; do find out, you have to open the file, try to locate the container signature and classify it by this signature)).

The same goes about file names stored in SQL Server. The database is totally OS-agnostic, and, even more obvious, the data itself "knows" nothing about the meaning of the content.

—SA