Question

我正在尝试与下面的2个查询相交，但是我收到了这个错误：

ProgrammingError :( ProgrammingError）（1064，“你的错误 SQL语法;查看与MySQL服务器对应的手册在'INTERSECT SELECT附近使用正确语法的版本 user_checkpoint.id AS user_checkpoint_id，user_checkpoint.user_'at 第4行“）'SELECT anon_1.user_checkpoint_id AS anon_1_user_checkpoint_id，anon_1.user_checkpoint_user_id AS anon_1_user_checkpoint_user_id，anon_1.user_checkpoint_checkpoint_id AS anon_1_user_checkpoint_checkpoint_id， anon_1.user_checkpoint_date_added AS anon_1_user_checkpoint_date_added \ nFROM（SELECT user_checkpoint.id AS user_checkpoint_id， user_checkpoint.user_id AS user_checkpoint_user_id， user_checkpoint.checkpoint_id AS user_checkpoint_checkpoint_id， user_checkpoint.date_added AS user_checkpoint_date_added \ nFROM user_checkpoint INNER JOIN检查点ON checkpoint.id = user_checkpoint.checkpoint_id INNER JOIN用户AS user_1 ON user_checkpoint.user_id = user_1.id INNER JOIN facebook_user AS facebook_user_1 ON facebook_user_1.id = user_1.facebook_user_id INNER JOIN friend_connection ON friend_connection.fb_user_to = facebook_user_1.id INNER JOIN facebook_user ON facebook_user.id = friend_connection.fb_user_from INNER JOIN用户ON user.facebook_user_id = facebook_user.id \ nWHERE user.id！=％s AND checkpoint.creator = user_1.id AND checkpoint.demo =％s INTERSECT SELECT user_checkpoint.id AS user_checkpoint_id， user_checkpoint.user_id AS user_checkpoint_user_id， user_checkpoint.checkpoint_id AS user_checkpoint_checkpoint_id， user_checkpoint.date_added AS user_checkpoint_date_added \ nFROM user_checkpoint INNER JOIN检查点ON checkpoint.id = user_checkpoint.checkpoint_id \ nWHERE checkpoint.creator！=％s AND checkpoint.demo =％s）AS anon_1 ORDER BY checkpoint.date_created DESC \ n LIMIT％s'（185L，0,185L，0,1）

    #get checkpoints from users with friends
    FriendUserCheckpoint, FriendFacebookUser, FriendUser = aliased(UserCheckpoint), aliased(FacebookUser), aliased(User)
    q = (db.session.query(UserCheckpoint).
         join(Checkpoint, Checkpoint.id == UserCheckpoint.checkpoint_id).
         join(FriendUser, FriendUser.id == UserCheckpoint.user_id).
         join(FriendFacebookUser, FriendFacebookUser.id == FriendUser.facebook_user_id).
         join(FriendConnection, FriendConnection.fb_user_to == FriendFacebookUser.id).
         join(FacebookUser, FacebookUser.id == FriendConnection.fb_user_from).
         join(User, User.facebook_user_id == FacebookUser.id).
         filter(User.id != user_obj.id).
         filter(Checkpoint.creator == FriendUser.id).
         filter(Checkpoint.demo == False)
         )

    #get checkpoints from users without friends
    p = (db.session.query(UserCheckpoint).
         join(Checkpoint, Checkpoint.id == UserCheckpoint.checkpoint_id).
         filter(Checkpoint.creator != user_obj.id).
         filter(Checkpoint.demo == False)
         )

    w = q.intersect(p)

    return w.order_by(desc(Checkpoint.date_created)).limit(limit).all()

我该如何解决？谢谢！

Answer 1

您的查询问题是order_by：您尝试按查询中不在的列进行排序。生成的SQL查询如下所示：

SELECT anon_1.col1, anon_1.col2, ...
FROM (
    SELECT  <UserCheckpoint columns>
    FROM    UserCheckpoint
    ... (joins, filters etc)


    INTERSECT

    SELECT  <UserCheckpoint columns>
    FROM    UserCheckpoint
    ... (joins, filters etc)
) anon_1
ORDER BY checkpoint.date_created DESC -- @note: here is the problem

如您所见，外部查询在其源表列表中没有checkpoint表（其中只包含一个表 anon_1）。删除order_by，我认为您的查询可以正常运行。

如果您需要order_by，请更改查询以返回date_created列，订购结果，然后删除该列：

q = (db.session.query(UserCheckpoint, Checkpoint.date_created).
...
p = (db.session.query(UserCheckpoint, Checkpoint.date_created).
...
return [uc for (uc, _) in w.order_by(desc(Checkpoint.date_created)).limit(limit).all()]

这个SQLAlchemy交叉有什么问题？

1 个答案: