When is the temporary database used?

I've been told that RDBMS ( SQL Server in this case ) make use of the temporary database to perform its internal job, for insta开发者_如何学运维nce when a SELECT count( column ) FROM foo query is performed.

What kind of queries / statements trigger the use of the temporary database?

background:

We are currently about to change the collation on our application database, but we have been told there might be problems if that database make use of the temporary database, because they will have different collation. The rationale is the temporary database is already being used by other applications.

So we want to identify what kind of queries may trigger temp db usage and see if they'll have any problem.

I've found this about when is the db used:

http://msdn.microsoft.com/en-us/library/ms190768.aspx