SQL调用表

Question

我的SQL查询：

SELECT 
    upd.*, 
    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 
     ) 
    OR EXISTS 
     (
     SELECT 
      * 
     FROM 
      topics as topic 
     WHERE 
      upd.uid = topic.uid 
      AND sub.uid = 118697835834 
    ) 
    ) 

ORDER BY upd.date DESC 
LIMIT 0, 15 

我得到一个错误，因为sub不能在subquery2，因为被称为其仅在subquery1 ...我如何能确保我可以称它为在子查询2以及？我是否必须在FROM之上的LEFT JOIN用户上面？

Unknown column 'sub.uid' in 'where clause' 

Answer 1

这些子查询是独立的子查询，不能共享任何数据。您需要在第二个子查询中进行连接才能获得您正在查找的结果。

另外，很有可能您不需要子查询就可以做到这一点，并且只使用连接速度更快。

Answer 2

我不认为你甚至需要子查询。可能的是，你可以加入做到这一切，类似这样的东西（虽然这只是估计不知道你的表）：

SELECT * 
FROM your_main_table upd 
INNER JOIN subscribers sub 
    ON upd.uid = sub.suid 
INNER JOIN topics topic 
    ON upd.uid = topic.uid 
WHERE sub.uid = :user 

Answer 3

免责声明：这不是测试，是几乎保证需要一些调整为它做你想要什么，但我想你想什么它是非常接近：

SELECT 
    upd.*, 
    usr.username AS username, 
    usr.profile_picture AS profile_picture, 
    COUNT(lik.id) AS liked_update, 
    COUNT(fav.id) AS favorited_update 
FROM 
    updates upd 
    INNER JOIN subscribers sub ON upd.uid = sub.suid 
    INNER JOIN topics topic ON upd.uid = topic.uid 
    LEFT JOIN users usr ON upd.uid = usr.uid 
    LEFT JOIN likes lik ON upd.update_id = lik.item_id AND upd.uid = lik.uid AND lik.type = 0 
    LEFT JOIN favorites fav ON upd.update_id = fav.item_id AND upd.uid = fav.uid AND fav.type = 0 
WHERE 
    upd.deleted = 0 
    AND (
     upd.uid = 118697835834 
     OR sub.uid = 118697835834 
    ) 
GROUP BY 
    upd.*, 
    usr.username, 
    usr.profile_picture 
ORDER BY upd.date DESC 
LIMIT 15 

Answer 4

我试图重新写你的查询，在保持原来的逻辑......但是，我很不清楚逻辑的某些部分，特别是主题。

SELECT DISTINCT 
    upd.*, -- Probably should not be doing * here... 
    usr.username AS `username`, 
    usr.profile_picture AS `profile_picture` 
    COUNT(DISTINCT lik.id) AS `liked_update`, 
    COUNT(DISTINCT fav.id) AS `favorited_update` 
FROM 
    updates AS upd 
    LEFT JOIN subscribers AS sub ON upd.uid = sub.suid 
    LEFT JOIN topics as topic ON upd.uid = topic.uid 
    LEFT JOIN users AS usr ON upd.uid = usr.uid 
    LEFT JOIN likes AS lik 
     ON lik.item_id = upd.update_id 
     AND lik.uid = upd.uid 
     AND lik.type = 0 
    LEFT JOIN favorites as fav 
     ON upd.update_id = fav.item_id 
     AND fav.uid = upd.uid 
     AND fav.type=0 
WHERE 
    upd.deleted = 0 
    AND (
     upd.uid = 118697835834 
     OR sub.uid = 118697835834 
     OR (topic.uid IS NOT NULL AND sub.uid = 118697835834) 
    ) 
GROUP BY upd..., usr.username, usr.profile_picture 
ORDER BY upd.date DESC 
LIMIT 0, 15