Which product has been ordered most number of times?
create table products (product_details varchar, product_id varchar, PRIMARY KEY (product_details)); create table order_items (product_id varchar, PRIMARY KEY (product_id))
select t2.product_details from order_items as t1 join products as t2 on t1.product_id = t2.product_id group by t1.product_id order by count(*) desc limit 1