题解 | #返回产品名称和每一项产品的总订单数#

select Products.prod_name, if(odIt.orders is NULl,0,odIt.orders)
from Products
left join (select prod_id,count(order_num)
as orders  from OrderItems
group by prod_id) as odIt on
Products.prod_id=odIt.prod_id
order by Products.prod_name asc