A DBA or developer might have a simple question – “Since when has my SQL Server instance been continuously running?”.
There are many places to look but the easiest is to look at the creation date of the system “tempdb” database.
SELECT create_date FROM sys.databases WHERE name = 'tempdb'
Now, to the question of why?
TempDB is special in a lot of respects. It gets recreated upon every restart so, the creation timestamp of that database is when the SQL Server instance was last started.
As you may know, among other things, anytime temporary tables are created, they get stored in the TempDB (and hence the commonly known “public toilet” analogy!).
On an unrelated note, unlike Oracle, where temporary space can be segmented between users if necessary, in SQL Server, there is no choice but for all users across databases in the instance to share the single TempDB. I hope that this changes in a newer version of SQL Server!
Here is how one would find out the same information for Oracle:
SELECT startup_time FROM v$instance