Show me the last names of all teachers.
select lastname from teachers
Show me the student grade in each classroom.
select distinct classroom,grade from list
Which classrooms do fifth grade students have?
select distinct classroom from list where grade = 5
Show me the teachers who teach in any of those classrooms.
select distinct t2.lastname from list as t1 join teachers as t2 on t1.classroom = t2.classroom where grade = 5