我需要帮助来创建一个SQL查询

Question

我使用asp.net创建个人网站，但我不熟悉SQL，需要帮助创建查询。

我有3个表有以下栏目：

UserInfos - 用户名，昵称，PictureAva和隐私。
UserFollower - FollowerId，FollowingId，Status。
PlaceFollower - 关注者ID，以下ID，日期，状态。

我需要从UserInfos表中选择每个人。

标准：

If Privacy = 0, I don't want this Row to be returned. 
If Privacy = 1, I need that the rows from UserInfos be returned when 
       UserInfos.UserID = UserFollower.FollowingId 
      and UserFollower.FollowerId = 2 
      and UserFollower.Status = 1, 
      only if PlaceFollower.FollowerId = UserFollower.FollowingId 
       and PlaceFollower.FollowingId = 1 
       and PlaceFollower.Status = 1 
       and PlaceFollower.Date = '17/07/2011'. 

    If Privacy = 2, I need that the rows from UserInfos be returned when 
      UserInfos.UserID = UserFollower.FollowingId 
      and UserFollower.FollowerId = 2 
      and UserFollower.Status = 1, 
     **OR** UserInfos.UserID = UserFollower.FollowerId 
      and UserFollower.FollowingId = 2 
      and UserFollower.Status = 1, 
      only if PlaceFollower.FollowerId = UserFollower.FollowingId 
      and PlaceFollower.FollowingId = 1 
      and PlaceFollower.Status = 1 
      and PlaceFollower.Date = '17/07/2011'. 

是否有可能做到这一点？

感谢您的帮助。

Answer 1

我会建议UNION。

select .. join .. where privacy=1 
UNION ALL 
select .. join .. where privacy=2