使用SUM在JOINed表中的列上进行SQL查询

Question

我在derby数据库中有两个表,我想一起查询.

Orders
+----+--------+--------------+------------+
| ID | UserID | PurchaseDate | TotalPrice |
+----+--------+--------------+------------+
|  1 |    1   | TIMESTAMP    |    7.00    |

OrderItems
+---------+-----------+----------+
| OrderID | ProductID | Quantity |
+---------+-----------+----------+
|    1    |      1    |     2    |

我想要一个查询来从订单表中返回订单上的所有信息以及与该订单关联的产品总数.

我试过这个认为它会工作,但得到错误 - "列引用'ID'无效.当SELECT列表包含至少一个聚合时,所有条目必须是有效的聚合表达式."

SELECT 
orders.ID, orders.UserID, orders.PurchaseDate, orders.TotalPrice, SUM(Quantity) 
AS productCount
FROM app.orders JOIN app.orderItems ON orders.ID=orderItems.OrderID 

Answer 1

SELECT 
app.orders.ID, app.orders.UserID, app.orders.PurchaseDate, app.orders.TotalPrice, SUM(app.orderItems.Quantity) 
AS productCount
FROM app.orders JOIN app.orderItems ON app.orders.ID=app.orderItems.OrderID 
group by app.orders.ID, app.orders.UserID, app.orders.PurchaseDate, app.orders.TotalPrice