List the names of actors and their musical names.
select t1.name,t2.name from actor as t1 join musical as t2 on t1.musical_id = t2.musical_id
What are the musical names that have two actors?
select t2.name from actor as t1 join musical as t2 on t1.musical_id = t2.musical_id group by t1.musical_id having count(*) = 2
What about at least three actors?
select t2.name from actor as t1 join musical as t2 on t1.musical_id = t2.musical_id group by t1.musical_id having count(*) >= 3