两种写法 1.where等联结： select cust_id, sum(quantity*item_price) total_ordered from Orders join OrderItems on Orders.order_num = OrderItems.order_num group by cust_id order by total_ordered desc 2.表内连接： select cust_id, sum(quantity*item_price) total_ordered from Orders, OrderItems where Orders...

两种方法（考虑sql运行顺序） 1.having： select order_num, sum(item_price*quantity)total_price  from OrderItems group by order_num  having sum(item_price*quantity)>=1000  order by order_num 2.子查询： select a.order_num,a.total_price from (select order_num, sum(item_price*quantity)tot...

select age,count(a.device_id)number  from (select substring(profile,12,2) age, device_id from user_submit)a group by age 考虑到sql的运行顺序，先from，子查询先出来age关键词，后续才能运行