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



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




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





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


select s.name, c.name, g.grade
from students s
join grades g on s.id = g.student_id
join courses c on c.id = g.course_id
where s.name = "Bart" or s.name = "Lisa";