Which architects have nationality 'American' or 'Canadian'?
select * from architect where nationality = 'American' or nationality = 'Canadian'
Find all mills that are built by these architects.
select * from mill as t1 join architect as t2 on t1.architect_id = t2.id where t2.nationality = 'American' or t2.nationality = 'Canadian'
What are the distinct types of these mills?
select distinct t1.type from mill as t1 join architect as t2 on t1.architect_id = t2.id where t2.nationality = 'American' or t2.nationality = 'Canadian'