帶有隱私條件檢查的查詢中的mysql查詢

Question

我有3張桌子。

myMembers
------------------------------------
id | username | privacy
------------------------------------
1  | userA    | 0
2  | userB    | 1
3  | userC    | 0
4  | userD    | 1

following
--------------------------------
id  | user_id  | follower_id
--------------------------------
1   | 2        | 1

posts
-------------------------------------
id  |  userID | username   | statusMsg
--------------------------------------
1   |  4      | userD    | Issac Newton is genius
2   |  2      | userB    | Newton Saw apple
3   |  3      | userC    | Newtonian Physics
4   |  1      | userA    | Calculus came from Sir Newton

有一個搜索字段。 當登錄的用戶在表“職位”中搜索“關鍵字”時，我想省略那些將其隱私設置為“ 1”並且WHERE搜索者沒有關注用戶B的用戶的結果。

查詢應在邏輯上執行此操作。

SELECT * from posts WHERE (match the keyword) 
            AND ( 
                if (poster's privacy (which is set in myMembers)==1){
                    if (seacher is following poster){
                        select this post
                    }
                }
                   else { select this post
                }
             )
                   LIMIT results to 5 rows

因此，對於關鍵字“牛頓”，如果userA正在搜索，則應返回“帖子”中的第2、3、4行。 如果userD正在搜索，則僅應返回“帖子”中的第1、3和4行，

基於隱私和以下編輯：標記以供將來搜索：mySql中WHERE子句中的IF條件

Answer 1

請嘗試以下查詢（也在SQL Fiddle上 ）：

SELECT p.id, p.user_id, m.username, m.privacy,
       searcher.username "Searcher", p.status_msg
  FROM posts p
  JOIN members m ON m.id = p.user_id
  LEFT JOIN following f ON p.user_id = f.user_id
  JOIN members searcher ON searcher.username = 'userA'
 WHERE (m.privacy = 0 OR (m.privacy = 1 AND f.follower_id = searcher.id)
                      OR m.id = searcher.id)
   AND p.status_msg LIKE '%New%'
 ORDER BY p.id
 LIMIT 5;

我從posts表中刪除了username段，因為這是多余的。 另外，我命名的表和列略有不同，因此查詢可能需要對架構進行外觀上的更改。

WHERE子句中的第一行是您要查找的那一行，它按以下順序選擇帖子：

1. 來自成員的第一篇帖子，沒有隱私；
2. 然后來自當前searcher成員的帖子;
3. 最后，成員本人的職位。

---

編輯：

該查詢使用原始標識符：

SELECT p.id, p.`userID`, m.username, m.privacy,
       searcher.username "Searcher", p.`statusMsg`
  FROM posts p
  JOIN `myMembers` m ON m.id = p.`userID`
  LEFT JOIN following f ON p.`userID` = f.user_id
  JOIN `myMembers` searcher ON searcher.username = 'userD'
 WHERE (m.privacy = 0 OR f.follower_id = searcher.id OR m.id = searcher.id)
   AND p.`statusMsg` LIKE '%New%'
 ORDER BY p.id
 LIMIT 5;

---

編輯2：

為了避免重復，以防有是從用戶數的追隨者posts表，加入和過濾條件應該改變方式如下（在SQL小提琴 ）：

SELECT p.id, p.user_id, m.username, m.privacy,
       searcher.username "Searcher", p.status_msg
  FROM posts p
  JOIN members m ON m.id = p.user_id
  JOIN members searcher ON searcher.username = 'userC'
  LEFT JOIN following f ON p.user_id = f.user_id
   AND follower_id = searcher.id
 WHERE (m.privacy = 0 OR (m.privacy = 1 AND f.id IS NOT NULL)
                      OR m.id = searcher.id)  
 ORDER BY p.id
 LIMIT 5;

Answer 2

嘗試這個：

SELECT a.*
FROM posts a
     LEFT JOIN (SELECT user_id
                FROM following a1
                     INNER JOIN myMembers b1
                       ON a1.follower_id = b1.id
                  WHERE a1.follower_id = 1 AND
                        b1.privacy = 1
                ) b
                ON a.userID = b.user_id AND
WHERE a.statusMsg LIKE '%search%' AND
      b.user_id IS NULL
LIMIT 5;

或沒有子查詢的更好方法：

SELECT a.*
FROM posts a
     LEFT JOIN myMembers b
         ON a.userID = b.id AND
            b.privacy = 1
     LEFT JOIN following c
         ON a.userID = c.user_id AND
            c.follower_id = 1
WHERE a.statusMsg LIKE '%search%' AND
      b.id IS NULL AND
      c.user_id IS NULL
LIMIT 5;

請參閱： SQL連接的直觀說明

Answer 3

請嘗試以下操作：

SET @my_user_id= 1;

SELECT * FROM posts p
INNER JOIN myMembers m ON p.user_id= m.id  
WHERE statusMsg LIKE '%'
AND privacy=0
AND user_id IN (SELECT follower_id FROM following f WHERE f.user_id=@my_user_id)
LIMIT 5