-- courses that Bart and Lisa both took --

select distinct c.name
from students s
join grades g on g.student_id = s.id
join courses c on c.id = g.course_id
join grades g2 on g2.course_id = g.course_id
join students s2 on s2.id = g2.student_id
where s.name = "Bart" and s2.name = "Lisa";


-- names of all teachers Bart has had --

select t.name, c.name
from students s
join grades g on g.student_id = s.id
join courses c on c.id = g.course_id
join teachers t on t.id = c.teacher_id
where s.name = "Bart";