How many car models are produced in the usa?
create table car_makers (id varchar, country varchar, PRIMARY KEY (id)); create table countries (countryid varchar, countryname varchar, PRIMARY KEY (countryid)); create table model_list (maker varchar, PRIMARY KEY (maker))
select count(*) from model_list as t1 join car_makers as t2 on t1.maker = t2.id join countries as t3 on t2.country = t3.countryid where t3.countryname = 'usa'