How many countries does each continent have? List the continent id, continent name and the number of countries.
create table countries (continent varchar, PRIMARY KEY (continent)); create table continents (contid varchar, continent varchar, PRIMARY KEY (contid))
select t1.contid, t1.continent, count(*) from continents as t1 join countries as t2 on t1.contid = t2.continent group by t1.contid