Can I find out which database is queried on the most?
You can use sys.dm_exec_sessions. This will only give you the count based on the current activity. You would need to store this historically if you wanted to trend it. Keep in mind that session ids of 50 or less are system sessions.

--By Database
select 
    db_name(database_id) DatabaseName
    ,count(session_id) as Session_count 
from sys.dm_exec_sessions
where
    session_id &gt; 50
group by
    database_id

--By Login
select 
    login_name
    ,count(session_id) as Session_count 
from sys.dm_exec_sessions
where
    session_id &gt; 50
group by
    login_name