select firstStud.name as FirstStudent, secondStud.name as SecondStudent, sports.name as Sport
from Students as firstStud join students as secondStud
on firstStud.id>secondStud.id
join sports on (
firstStud.id in(
select student_id from student_sport
where sportGroup_id in(
select id from sportGroups where sportGroups.sport_id=sports.id))
and (secondStud.id in (
select student_id from student_sport
where sportGroup_id in(
select id from sportGroups where sportGroups.sport_id=sports.id ) )))
where firstStud.id in(
select student_id from student_sport where sportGroup_id in(
select sportGroup_id from student_sport where student_id=secondStud.id))
order by sport;