Counts the number of active instructors in moodle.

count_instructors.sql

select count(distinct(ue.userid))  from mdl_user_enrolments ue
  join mdl_enrol e on (ue.enrolid=e.id)
  join mdl_course c on (c.id=e.courseid)
  join (select * from mdl_context where contextlevel=50) ct on (ct.instanceid=c.id)
  join (select * from mdl_role_assignments where component='enrol_engine') ra on (ra.contextid=ct.id and ue.userid=ra.userid)
  join mdl_role r on (ra.roleid = r.id)
  where c.idnumber like '%-<insert_quarter_suffix_here>'
  and c.visible=1
  and ue.status=0
  and r.name = 'Instructor'
-- Here, "engine" is used to only select automatically provisioned users
--  and e.enrol like 'engine'
  order by c.idnumber