我無法查詢

Question

我正在嘗試進行查詢，但它沒有顯示任何結果。我的表是：

TABLE teacher_student_conn: 
    id, teacher_id, student_id, created_at 
TABLE users: 
    user_id, username, password, school_id, class, division, role_id, deactivated_at 
TABLE schools: 
    school_id, school_name 

我想表明我的只有這些學生是在老師的學校，他不教他們 - 我把老師從$this->uri->segment(3) ADN學校 - 從$this->uri->segment(4)。它必須顯示這些學生，因爲管理員可以將它們添加到教師。 我不知道如何讓我的查詢向我展示這些在老師的學校裏的學生，他不教他們。 我對查詢嘗試：

public function select_students() { 
 
    
 
     $this->db->select('users.user_id, users.username, users.school_id, users.class, users.division, users.role_id, schools.school_name, schools.region,class_divisions.division'); 
 
     $this->db->from('users');  
 

 
     $this->db->join('teacher_student_conn','teacher_student_conn.student_id=users.user_id','left'); 
 
     $this->db->join('teacher_student_conn AS T','T.teacher_id=users.user_id','left'); 
 

 
     $this->db->join('class_divisions','class_divisions.id=users.division','left'); 
 
     $this->db->join('schools','schools.school_id=users.school_id','left'); 
 
     $this->db->where('(users.deactivated_at = "0000-00-00 00:00:00" OR users.deactivated_at IS NULL) AND users.role_id = 1 '); 
 

 
     $this->db->where('users.school_id', $this->uri->segment(4)); 
 
     $this->db->where('teacher_student_conn.teacher_id', $this->uri->segment(3)); 
 
     $this->db->where("teacher_student_conn.student_id IS NULL"); 
 

 
      
 
     $result=$this->db->get(); 
 
      return $result->result(); 
 
}

後呼應$這個 - > DB-> last_query（）;它顯示我：

SELECT users.user_id, users.username, users.school_id, users.class, users.division, users.role_id, schools.school_name, schools.region,class_divisions.division FROM users LEFT JOIN teacher_student_conn ON teacher_student_conn.student_id=users.user_id LEFT JOIN teacher_student_conn as T ON T.teacher_id=users.user_id LEFT JOIN class_divisions ON class_divisions.id=users.division LEFT JOIN schools ON schools.school_id=users.school_id WHERE (users.deactivated_at = '0000-00-00 00:00:00' OR users.deactivated_at IS NULL) AND users.role_id = 1 AND users.school_id = 2 AND teacher_student_conn.teacher_id = 10 AND

現在我用這個查詢：

public function select_students() { 
 
    $query=("SELECT users.user_id, users.username, users.school_id, users.class, users.division, users.role_id, schools.school_name, schools.region,class_divisions.division FROM users 
 
    LEFT JOIN teacher_student_conn ON teacher_student_conn.student_id=users.user_id 
 
    LEFT JOIN teacher_student_conn as T ON T.teacher_id=users.user_id 
 
    LEFT JOIN class_divisions ON class_divisions.id=users.division 
 
    LEFT JOIN schools ON schools.school_id=users.school_id 
 
    WHERE (users.deactivated_at = '0000-00-00 00:00:00' OR users.deactivated_at IS NULL) AND users.role_id = 1 AND 
 
    users.school_id = 2 "); 
 
    $this->db->where('teacher_student_conn.student_id', NULL); 
 
    $result = $this->db->query($query); 
 
    echo $this->db->last_query(); 
 
      return $result->result(); 
 

 
}

我找到了解決辦法：

$teacher=$this->uri->segment(3); 
 
    $query=("SELECT users.user_id, users.username, users.school_id, users.class, users.division, users.role_id, schools.school_name, schools.region,class_divisions.division FROM users 
 
    LEFT JOIN teacher_student_conn ON teacher_student_conn.student_id=users.user_id 
 
    AND teacher_student_conn.teacher_id = $teacher 
 
    LEFT JOIN teacher_student_conn as T ON T.teacher_id=users.user_id 
 
    LEFT JOIN class_divisions ON class_divisions.id=users.division 
 
    LEFT JOIN schools ON schools.school_id=users.school_id 
 
    WHERE (users.deactivated_at = '0000-00-00 00:00:00' OR users.deactivated_at IS NULL) AND users.role_id = 1 AND 
 
    users.school_id = 2 AND teacher_student_conn.student_id IS NULL"); 
 

 
    
 
    $result = $this->db->query($query); 
 
    echo $this->db->last_query(); 
 
      return $result->result(); 
 

 
}

Answer 1

這只是sql查詢格式，打印您的查詢並粘貼到PHPmyadmin SQL或echo $ this-> db-> last_query（）;.

public function select_students() { 

     $query = "SELECT users.user_id, users.username, users.school_id, users.class, users.division, users.role_id, schools.school_name, schools.region,class_divisions.division FROM users" 
       . "LEFT JOIN teacher_student_conn ON teacher_student_conn.student_id=users.user_id" 
       . "LEFT JOIN teacher_student_conn as T ON T.teacher_id=users.user_id" 
       . "LEFT JOIN class_divisions ON class_divisions.id=users.division" 
       . "LEFT JOIN schools ON schools.school_id=users.school_id" 
       . "WHERE (users.deactivated_at = '0000-00-00 00:00:00' OR users.deactivated_at IS NULL) AND users.role_id = 1 AND " 
       . "users.school_id = ".$this->uri->segment(4)." AND teacher_student_conn.teacher_id = ".$this->uri->segment(4)." AND teacher_student_conn.student_id IS NULL"; 
     $result = $this->db->query($query); 

     return $result->result();    
}