products表和order_items表的数据如下: products: product_id product_name 1 intel c/8/hq 2 cpu d300 3 hd 8gb/i 4 hd 12gb /r order_items: order_id product_id qty unit_price 11 1 10 100 22 2 15 120 33 3 10 50 44 1 5 10 66 2 20 125 select p.product_id,i.item_cnt from (select product_id,count(*) item_cnt from order_items group by product_id) i right outer join products p on i.product_id=p.product_id; 这条sql语句执行的结果是: