Question

我有以下表格：

具有主键和用户名的用户，例如

ID    Username       
1     Fred        
2     John       
3     Jack

具有主键和事件名称的事件

ID    Eventname       
1     Ferrari Road Show
2     Flower Show

UserStatusUpdates表，其中包含主键，状态更新和用户标识（外键）

ID   UserID   UserStatus
1    1        Really Good
2    1        Leaving Now
3    2        I concur

具有主键和两个外键（事件主键和用户主键）的事件参加者表

ID UserID   EventID
1  1        1
2  2        1
3  3        1

我遇到的问题是我需要返回所有活动参与者及其最新状态更新，但有时用户实际上没有进行状态更新。

这就是我的查询：

SELECT EventAttendee.*, Users.UserName,Users.USERS_ID, 
Users.ThumbnailPic,
Users.CountryName,
ISNULL(UserStatusUpdates.UserStatus,'No Updates')AS LastUpdate,
UserStatusUpdates.MediaTypeID,UserStatusUpdates.USERSTATUS_ID,(UserStatusUpdates.AddDate)

FROM EventAttendee
JOIN Users ON Events.UserID = Users.USERS_ID
OUTER APPLY  (SELECT TOP 1 UserStatusUpdates.UserStatus,UserStatusUpdates.MediaTypeID,
UserStatusUpdates.USERSTATUS_ID,UserStatusUpdates.AddDate, UserStatusUpdates.UserID
  FROM UserStatusUpdates  where UserStatusUpdates.UserID = Users.USERS_ID
ORDER BY AddDate DESC) AS UserStatusUpdates WHERE UserStatusUpdates.UserID = EventAttendee.UserID

WHERE EventAttendee.EventID = @EventID 
AND Users.bDeleted = 'False' 
AND Users.bSuspended =  'False'
END

如何找回可能未进行更新的用户？

Answer 1

您的查询有多个where子句，并且您已在子查询中指定UserStatusUpdates.UserID = Users.USERS_ID联接。试试这个：

SELECT 
  EventAttendee.*, 
  Users.UserName,Users.USERS_ID, 
  Users.ThumbnailPic,
  Users.CountryName,
  ISNULL(UserStatusUpdates.UserStatus,'No Updates') AS LastUpdate,
  UserStatusUpdates.MediaTypeID,
  UserStatusUpdates.USERSTATUS_ID,
  UserStatusUpdates.AddDate
FROM 
  EventAttendee
  JOIN Users ON 
    Events.UserID = Users.USERS_ID
  OUTER APPLY (
    SELECT TOP 1 
      UserStatusUpdates.UserStatus,
      UserStatusUpdates.MediaTypeID,
      UserStatusUpdates.USERSTATUS_ID,
      UserStatusUpdates.AddDate,
      UserStatusUpdates.UserID
    FROM 
      UserStatusUpdates  
    WHERE 
      UserStatusUpdates.UserID = Users.USERS_ID
    ORDER BY 
      AddDate DESC
  ) AS UserStatusUpdates 
WHERE 
  EventAttendee.EventID = @EventID 
  AND Users.bDeleted = 'False' 
  AND Users.bSuspended =  'False'
END

使用外部应用返回空值

1 个答案: