Returns the numeric user ID for the specified user name.
SUSER_ID( [ user-name ] )
user-name The user name for the user ID you are searching for.
INT
If you do not specify user-name, the ID of the current user is returned.
SQL/2008 Transact-SQL extension.
The following statement returns the ID for the GROUPO user.
SELECT SUSER_ID( 'GROUPO' );