What are the names and id of courses having at most 2 sections?
create table courses (course_name varchar, course_id varchar, PRIMARY KEY (course_name)); create table sections (course_id varchar, PRIMARY KEY (course_id))
select t1.course_name, t1.course_id from courses as t1 join sections as t2 on t1.course_id = t2.course_id group by t1.course_id having count(*) <= 2