Question: For each product which has problems, what are the number of problems and the product id?
Schema: create table problems (product_id varchar, PRIMARY KEY (product_id)); create table product (product_id varchar, PRIMARY KEY (product_id))
SQL: 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