Convert query in eloquent relationship laravel

Question

I have 5 tables students,teachers,subjects,student_subject,subject_teacher student have many to many relationship with subject similarly teacher have many to many relation with subject .

students table

id | name | email

teachers table

id | name | email

subjects table

id | name

subject_teacher table:

id | teacher_id | subject_id

student_subject table:

id | student_id | subject_id

above is my database structure In models of Student,Teacher,Subject i define many to many relation. So if i want to get subject of teacher i simply do Teacher::find(1)->subjects()->get(). In my current database structure i have not direct relation between students and teachers but i want to get all students of teacher i can do this with query like

 Student::join('student_subject', 'students.id', '=', 'student_subject.student_id')
 ->join('subject_teacher', 'student_subject.subject_id', '=', 'subject_teacher.subject_id')
 ->where('subject_teacher.teacher_id', '=',1)
  ->groupBy('students.name');

My problem i don't want query i want to do this with eloquent what i do what i will change in my relationship please help me

Note: I don't want to change in my database structure. I know if it is possible with query then it will surely possible with eloquent.

Possible duplicate of [HasManyThrough with one-to-many relationship](http://stackoverflow.com/questions/23788844/hasmanythrough-with-one-to-many-relationship) — Fabio Antunes, Mar 30 '16 at 09:40
You want a has many through relationship but you can't have that because your relationships are all many to many — Fabio Antunes, Mar 30 '16 at 10:39
https://laravel.com/docs/master/eloquent-relationships#has-many-through — Fabio Antunes, Mar 30 '16 at 10:42
I read that but in my case i have pivot table so how i can apply has many through relation in pivot table ?? — Muhammad Umar, Mar 30 '16 at 10:47
As far as I know there's no way that you can solve this using eloquent, the only thing that you might do is eager loading a nested relationship and then iterate for each subject and then iterate again for eahc teacher, something like `Student::with('subject.teacher')` — Fabio Antunes, Mar 30 '16 at 11:03

The Alpha · Answer 1 · 2016-03-30T14:55:58.010

You don't need to change your table's strtucture to use Eloquent. All you need is to create Eloquent models and defime relationships. So, let's create Models for students, teachers and subjects at first.

Student Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Student extends Model {

    public function subjects()
    {
        return $this->belongsToMany(Subject::class);
    }

}

Teacher Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Teacher extends Model {

    public function subjects()
    {
        return $this->belongsToMany(Subject::class);
    }

}

Subject Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Subject extends Model {

    public function students()
    {
        return $this->belongsToMany(Student::class);
    }

    public function teachers()
    {
        return $this->belongsToMany(Teacher::class);
    }

}

Now you can use something like this:

// Get all students with related subjects
$studentsWithSubjects = \App\Student::with('subjects')->get();

// Get student with id 1 with related subjects
$student1WithSubjects = \App\Student::with('subjects')->find(1);

Use same rules with Teacher model. Hope it helps to get you started.

Update:

Well, if you want to make a relation between Teacher & Student model using a many-to-many relationship then you need to create another pivot table using id, 'student_id' and teacher_id and then define relationship methods in both Teacher and Student model so you can use relationship method from both sides, for example:

// In Student Model
public function teachers()
{
    return $this->belongsToMany(Teacher::class);
}

// In Teacher Model
public function students()
{
    return $this->belongsToMany(Student::class);
}

So now you'll be able to use something like this:

$teacher1WithStudents = \App\Teacher::with('students')->find(1);
$student1WithTeachers = \App\Student::with('teachers')->find(1);

I think you don't understand my prolem . I do the same thing with my model that you mentiond . I can easily get student subject and teacher subject but i want to get student->teacher or teacher->student . I don't know what i do . If you know please help me — Muhammad Umar, Mar 30 '16 at 10:03

score 0 · Answer 2 · answered Mar 30 '16 at 15:31

I want to re-construct the question first:

There are teachers giving classes on some subjects. There are students taking classes on some subjects.

A student's teachers are the teachers giving classes on the subjects student taking.

A teacher's students are the students taking classes on the subjects teacher giving.

If that is correct I suggest you to use eager loading.

As an example, to get the student with id 1:

$student = App\Students::with(['subjects.teachers'])->find(1)->get();

Then you can do a foreach on

$student->subjects

And every subject will get teachers.

Attention! If you have just one subject for each teacher, use belongs to and has many relations.

When you get the general idea about eager loading, you can use some other query constraints on the eager loading query to get directly what you want.

Check the eager loading section here : https://laravel.com/docs/5.2/eloquent-relationships#querying-relations

Convert query in eloquent relationship laravel

2 Answers2

Update: