User table

id | name | user_type | email           | password
1  | John | 1         | john@gmail.com  | something
2  | Roy  | 1         | roy@gmail.com   | something
3  | Rax  | 1         | Rax@gmail.com   | something
4  | Ren  | 1         | ren@gmail.com   | something

AssignUser Table

id | user_id      | assign_to_math | assign_to_chemistry
1  | 3            | 2               | 1
2  | 4            | 1               | 2

public function getInfoFormathTutor(){
        return $this->hasOne('AppAssignUser', 'id', 'assign_to_math');
    }