Código PHP:
$registros=mysql_query("select c2.fullname, u.id, u.username, c.fullname, c.shortname
from mdl_user_enrolments as ue
inner join mdl_enrol as e on (e.courseid=4 and e.enrol = 'meta' and e.id = ue.enrolid)
inner join mdl_course as c on (e.customint1 = c.id)
inner join mdl_user as u on (ue.userid = u.id)
inner join mdl_course c2 on (e.courseid = c2.id)
order by c.shortname",$conexion) or die("Problemas en el select:".mysql_error());
while ($registro = mysql_fetch_array($registros)){
$sql2=mysql_query("INSERT INTO `moodle`.`mdl_groups_members` (`groupid`, `userid`)
VALUES (15, "AQUI_MIS_ID");",$conexion) or die ("Problemas en insertar usuarios a grupos:".mysql_error());
}