MySQL 连接两个表并求和？

Question

我有 2 个表 - orders 和 orderdetail。

我需要将它们连接在一起并显示总数。我可以加入他们，但我如何计算总数？

SELECT * 
FROM Orders as o 
INNER JOIN OrderDetails as od on o.order_id = od.order_id 
WHERE o.table_id = 1

Answer 1

 select a.order_id,
 order_date,
 order_status,
 table_id,
 item_id,
 item_price,
 quantity,
 b.item_price*b.quantity as total
 from dbo.orders as a inner join dbo.orderdetails as b
 on a.order_id=b.order_id
 WHERE table_id = 1

Update : as you mentioned in comment if you want a computed column which automatically multiply quantity and item_price, then you need execute this query :

  ALTER TABLE dbo.orderdetails ADD Total AS (quantity* item_price);