How many products do not have any problems?
select count(*) from product where product_id not in (select product_id from problems)
What are they?
select product_id from product where product_id not in (select product_id from problems)
Show all the different ids of the products other than these!
select distinct product_id from problems
Also provide the number of problems they each have!
select count(*), t2.product_id from problems as t1 join product as t2 on t1.product_id = t2.product_id group by t2.product_id