MySQL三維三角查詢

Question

我有一個團隊，學校和作業數據庫。在選擇作業後，學校（用戶無論如何）都可以將一個小組添加到作業中，以便他們可以開始作業。 ER圖如下所示： 重要事項：即使數據庫的設置建議不然，團隊< - >分配關係是1：N。一個團隊只能處理一項任務。這是通過ORM系統控制的。

現在這裏有一個問題：數據庫中有團隊負責不屬於他們學校的作業：學校選擇作業，創建團隊並刪除他們的作業選擇。我需要找到這種情況下的學校（身份證，姓名）。

到目前爲止，我已經成功地拿出了最好的查詢是：

SELECT schools.school_id, schools.name 
FROM schools 
LEFT JOIN teams ON schools.school_id = teams.school_id 
LEFT JOIN assignment_teams ON teams.team_id = assignment_teams.team_id 
LEFT JOIN assignment_schools ON schools.school_id = assignment_schools.school_id 
WHERE assignment_teams.assignment_id != assignment_schools.assignment_id; 

但當我手工檢查的結果這是行不通的。我在找什麼正確的查詢？

Answer 1

其中一個應該工作，但我不知道這是最快：

1. SELECT school_id 
       FROM teams 
       INNER JOIN assignment_teams ON teams.team_id = assignment_teams.team_id 
       LEFT JOIN assignment_schools ON assignment_schools.school_id = teams.school_id AND assignment_schools.assignment_id = assignment_teams.assignment_id 
       WHERE assignment_schools.school_id IS NULL 
   

2. SELECT school_id 
       FROM teams 
       INNER JOIN assignment_teams ON teams.team_id = assignment_teams.team_id 
       WHERE assignment_id NOT IN (
       SELECT assignment_id 
        FROM assignment_schools 
        WHERE assignment_schools.school_id = teams.school_id 
   ) 
   

3. SELECT school_id 
       FROM teams 
       INNER JOIN assignment_teams ON teams.team_id = assignment_teams.team_id 
       WHERE NOT EXISTS (
       SELECT * 
        FROM assignment_schools 
        WHERE assignment_schools.school_id = teams.school_id 
        AND assignment_schools.assignment_id = assignment_teams.assignment_id 
   )