Question

查询：

            (
                SELECT
                    upd.uid,
                    upd.update_id,
                    upd.update,
                    upd.date,
                    upd.type,
                    upd.total_likes,
                    upd.total_comments,
                    upd.deleted,
                    usr.username AS `username`,
                    usr.profile_picture AS `profile_picture`
                    ,(
                        SELECT
                            COUNT(lik.id)
                        FROM
                            likes as lik
                        WHERE
                            upd.update_id = lik.item_id
                            AND
                            lik.uid = 118697835834
                            AND lik.type=0
                    ) as liked_update,
                    (
                        SELECT
                            COUNT(fav.id)
                        FROM
                            favorites as fav
                        WHERE
                            upd.update_id = fav.item_id
                            AND
                            fav.uid = 118697835834
                            AND fav.type=0
                    ) as favorited_update

                FROM 
                    updates AS upd
                    LEFT JOIN 
                        users AS usr
                            ON upd.uid = usr.uid
                WHERE
                    upd.deleted=0
                  AND
                    (
                        upd.uid=118697835834
                           OR EXISTS
                          (
                              SELECT *
                            FROM
                                subscribers AS sub
                            WHERE
                                upd.uid = sub.suid
                                  AND sub.uid = 118697835834
                          )
                    )

            )
            UNION
            (
                SELECT
                    topic.uid,
                    topic.tid,
                    topic.title,
                    topic.body,
                    topic.total_likes,
                    topic.total_replies,
                    topic.views,
                    topic.date,
                    usr.username AS `username`,
                    usr.profile_picture AS `profile_picture`
                    ,(
                        SELECT
                            COUNT(lik.id)
                        FROM
                            likes as lik
                        WHERE
                            topic.update_id = lik.item_id
                            AND
                            lik.uid = 118697835834
                            AND lik.type=1
                    ) as liked_update,
                    (
                        SELECT
                            COUNT(fav.id)
                        FROM
                            favorites as fav
                        WHERE
                            topic.update_id = fav.item_id
                            AND
                            fav.uid = 118697835834
                            AND fav.type=1
                    ) as favorited_update

                FROM 
                    topics AS topic
                    LEFT JOIN 
                        users AS usr
                            ON topic.uid = usr.uid
                WHERE
                    topic.deleted=0
                  AND
                    (
                        topic.uid=118697835834
                           OR EXISTS
                          (
                              SELECT *
                            FROM
                                subscribers AS sub
                            WHERE
                                topic.uid = sub.suid
                                  AND sub.uid = 118697835834
                          )
                    )

            )
            ORDER BY date DESC

我添加了UNION ( SELECT )并且查询需要永远加载，最后它会停止返回blank page ...

删除UNION ( SELECT )可以正常工作......

Answer 1

确定所有评论后，请说明您为使脚本正常工作所做的更改。

根据您对来自同一列的两个表的数据的评论，因为您已通过使用UNION告诉引擎执行此操作。如果你想要它们在单独的列中，你需要在它们之间放置Null：

SELECT
    upd.uid,
    upd.update_id,
    upd.update,
    upd.date,
    upd.type,
    upd.total_likes,
    upd.total_comments,
    upd.deleted,
    null AS `topicuid`,
    null AS `topictid`,
    null AS `topictitle`,
    null AS `topicbody`,
    null AS `topictotal_likes`,
    null AS `topictotal_replies`,
    null AS `topicviews`,
    null AS `topicdate`,
    usr.username AS `username`,
    usr.profile_picture AS `profile_picture`,
    (SELECT COUNT(lik.id) FROM likes as lik WHERE upd.update_id = lik.item_id AND lik.uid = 118697835834 AND lik.type=0) as liked_update,
    (SELECT COUNT(fav.id) FROM favorites as fav WHERE upd.update_id = fav.item_id AND fav.uid = 118697835834 AND fav.type=0) as favorited_update
FROM
    ......
UNION ALL
SELECT
    null AS `upd.uid`,
    null AS `upd.update_id`,
    null AS `upd.update`,
    null AS `upd.date`,
    null AS `upd.type`,
    null AS `upd.total_likes`,
    null AS `upd.total_comments`,
    null AS `upd.deleted`,
    topic.uid,
    topic.tid,
    topic.title,
    topic.body,
    topic.total_likes,
    topic.total_replies,
    topic.views,
    topic.date,
    usr.username AS `username`,
    usr.profile_picture AS `profile_picture`,
    (SELECT COUNT(lik.id) FROM likes as lik WHERE topic.update_id = lik.item_id AND lik.uid = 118697835834 AND lik.type=1) as liked_update,
    (SELECT COUNT(fav.id) FROM favorites as fav WHERE topic.update_id = fav.item_id AND fav.uid = 118697835834 AND fav.type=1) as favorited_update

您可能需要对列名做更多的工作，但是您应该到达那里。我没有对这个问题进行投票，但我可能应该这样做。您应该了解UNION运算符对两个或多个查询实际执行的操作。

Answer 2

当您使用UNION时，您必须具有完全相同的结果“列格式，名称，...”，因此您在查询upd.total_comments的顶部作为total_comments，并且您将topic.total_replies作为{ {1}}这些是不同的名字。希望您理解我尝试解释的内容，如果不是，请访问here，以便更好地解释。

sql UNION中断查询

2 个答案: