The information you're looking for is held in the Site Admin database's SESSIONS_HISTORY table. You can run your SQL queries against this table which contains these fields:
- **Session ID** (int): Unique ID (Primary key).
- **Start_Time** (DateTime): Date and time that the user logged in.
- **End_Time** (DateTime): Date and time that the user logged out. If null it means the session is active.
- **Domain_Name** (Varchar 255): Domain of the project which the user logged in to.
- **Project_Name** (Varchar 255): Project that the user logged in to.
- **User_Name** (Varchar 60): User name.
- **Client_Type** (Varchar 50): Client type (either a normal user or a QTP test execution client).
So, for example, if you wanted to report on how many users logged in for a specific date:
WHERE START_TIME >= '02-FEB-13?
group by user_name
order by count(*) desc