Show all product names without an order.
create table products (product_name varchar, product_id varchar, PRIMARY KEY (product_name)); create table order_items (product_id varchar, PRIMARY KEY (product_id)); create table products (product_name varchar, PRIMARY KEY (product_name))
select product_name from products except select t1.product_name from products as t1 join order_items as t2 on t1.product_id = t2.product_id