基本查询的聚合函数错误

Question

我的数据库是基于电影院的，我正在尝试查询显示为每部电影放映购买的门票数量。此查询涉及的表是 Bookings、Screenings 和 Movies。

这是 Bookings 表：

放映表：

还有电影表：

到目前为止，我已经设法使查询达到了能够显示每次放映的预订量的程度，但这并没有考虑到单次预订可能会购买多张票的事实，因此 Bookings 中的 Quantity 列：

这是让我走到这一步的 SQL 代码：

SELECT Count(Bookings.[Booking ID]) 
AS [Bookings Per Screening], 
Bookings.[Screening ID], 
Movies.Movie 
FROM Movies 
INNER JOIN (Screenings 
INNER JOIN Bookings 
ON 
Screenings.[Screening ID] = Bookings.[Screening ID]) 
ON Movies.[Movie ID] = Screenings.[Movie ID] 
GROUP BY 
Bookings.[Screening ID], Movies.Movie, 
Screenings.[Movie ID], Movies.[Movie ID];

但是，当我尝试添加一个字段来计算每次放映购买的门票数量，而不是每次放映的预订量时，每次放映都会显示多行：

这是产生该代码的代码：

SELECT Count(Bookings.[Booking ID]) 
AS [Bookings Per Screening], 
Bookings.[Screening ID], 
Movies.Movie, 
[Bookings Per Screening]*[Quantity] AS [Ticket Per Booking], 
Bookings.Quantity
FROM Movies 
INNER JOIN (Screenings 
INNER JOIN Bookings 
ON Screenings.[Screening ID] = Bookings.[Screening ID]) 
ON Movies.[Movie ID] = Screenings.[Movie ID]
GROUP BY Bookings.[Screening ID], Movies.Movie, 
Screenings.[Movie ID], Movies.[Movie ID], Bookings.Quantity;

我必须怎么做才能让它工作？

Answer 1

停止尝试计算 Bookings 并将它们相乘。

每一行已经告诉您售出了多少张门票。

SELECT
  [Screenings].[Screening Date],
  [Screenings].[Screening Time],
  [Movie].[Movie],
  SUM([Bookings].[Quantity]) AS [Seats Bought]
FROM
  [Bookings]
INNER JOIN
  [Screenings]
ON [Bookings].[Screening ID] = [Screenings].[Screening ID]
INNER JOIN
   [Movies]
ON  [Movies].[Movie ID] = [Screenings].[Movie ID]
GROUP BY
  [Screenings].[Screening Date],
  [Screenings].[Screening Time],
  [Movie].[Movie];

Answer 2

在 SELECT 语句中，Movies.Quantity 和 [Bookings Per Screening]*[Quantity] AS [Tickets per Screening] 之间似乎缺少 ,。