MySQL三维三角查询

Question

我有一个团队，学校和作业数据库。在选择作业后，学校（用户无论如何）都可以将一个小组添加到作业中，以便他们可以开始作业。 ER图如下所示： 重要事项：即使数据库的设置建议不然，团队< - >分配关系是1：N。一个团队只能处理一项任务。这是通过ORM系统控制的。

现在这里有一个问题：数据库中有团队负责不属于他们学校的作业：学校选择作业，创建团队并删除他们的作业选择。我需要找到这种情况下的学校（身份证，姓名）。

到目前为止，我已经成功地拿出了最好的查询是：

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; 

但当我手工检查的结果这是行不通的。我在找什么正确的查询？

Answer 1

其中一个应该工作，但我不知道这是最快：

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 
   )