Moodle SQL

Handy queries for Moodle.

Count number of users who are are in courses:

select count(distinct ra.userid) from mdl_role_assignments ra,mdl_context c
where ra.contextid=c.id and c.contextlevel=50

Show users who are users in Moodle, but not  in a class:

select * from mdl_user where not exists (select * from mdl_user_lastaccess where mdl_user.id =  mdl_user_lastaccess.id);

Number of users who have classes: