How many lessons taught by staff whose first name has letter 'a' in it?
create table lessons (staff_id varchar, PRIMARY KEY (staff_id)); create table staff (staff_id varchar, first_name varchar, PRIMARY KEY (staff_id))
select count(*) from lessons as t1 join staff as t2 on t1.staff_id = t2.staff_id where t2.first_name like "%a%"