查询三个表什么都没输出

Question

我有三个表，如下面的屏幕截图所示：

但是当我想执行以下查询时，即使所有三个表中都有数据，我也没有得到任何结果：

以下是生成的代码：

SELECT Clients.ClientID, Clients.FirstName, Clients.Surname, Clients.Internal, Clients.Organisation, Clients.LandlineNo, Clients.MobileNo, Clients.Address1, Clients.Town, 
              Clients.Postcode, Clients.Email, Clients.NHS, Clients.PurchaseOrderNumber, Bookings.Date, Bookings.Timebegan, Bookings.Timefinished, Bookings.Price, 
              Bookings.Repeats, Bookings.Rweeks, Bookings.Rdays, Bookings.Rmonths, Bookings.Occurrences, Rooms.Roomname
FROM     Clients INNER JOIN
              Bookings ON Clients.ClientID = Bookings.ClientID INNER JOIN
              Rooms ON Bookings.RoomID = Rooms.RoomID

Answer 1

Try

SELECT *
FROM     Clients LEFT OUTER JOIN
         Bookings ON Clients.ClientID = Bookings.ClientID 
         LEFT OUTER JOIN Rooms ON Bookings.RoomID = Rooms.RoomID

请参阅Visual Explanation of SQL Join以更好地了解使用方法

如果性能问题，还有其他一些方法。