SQL調用表

Question

我的SQL查詢：

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 

我得到一個錯誤，因爲sub不能在subquery2，因爲被稱爲其僅在subquery1 ...我如何能確保我可以稱它爲在子查詢2以及？我是否必須在FROM之上的LEFT JOIN用戶上面？

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

Answer 1

這些子查詢是獨立的子查詢，不能共享任何數據。您需要在第二個子查詢中進行連接才能獲得您正在查找的結果。

另外，很有可能您不需要子查詢就可以做到這一點，並且只使用連接速度更快。

Answer 2

我不認爲你甚至需要子查詢。可能的是，你可以加入做到這一切，類似這樣的東西（雖然這只是估計不知道你的表）：

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

免責聲明：這不是測試，是幾乎保證需要一些調整爲它做你想要什麼，但我想你想什麼它是非常接近：

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

我試圖重新寫你的查詢，在保持原來的邏輯......但是，我很不清楚邏輯的某些部分，特別是主題。

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