Eloquent Relationships Explained Clearly (Laravel 12

1. Why Eloquent Relationships?
Instead of writing raw SQL JOIN every time, Laravel lets you say:

 bash

$posts = User::find(1)->posts;        // automatically gets all posts of that user
$author = Post::find(5)->author;      // instantly gets the user who wrote the post

This magic is done by Eloquent Relationships.

2. The 6 Main Relationships You Must Know

Relationship	Meaning (Real Life)	Method in Model	Example
One to One	One user → one profile	hasOne() / belongsTo()	User → Profile
One to Many	One user → many posts	hasMany() / belongsTo()	User → Posts
Many to Many	One student → many courses, one course → many students	belongsToMany()	Student Course
Has One Through	Country → one capital (through capital table)	hasOneThrough()	Country → Capital
Has Many Through	Country → many citizens (through users table)	hasManyThrough()	Country → Users
Polymorphic	One image → belongs to Post or Product	morphTo() / morphMany() / morphToMany()	Image → Post/Product

3. Real-Life Examples with Code (Laravel 12)
1. One to Many (Most Common)

 bash

// User.php
class User extends Model
{
    public function posts()                  // A user has many posts
    {
        return $this->hasMany(Post::class);
    }
}

// Post.php
class Post extends Model
{
    public function user()                    // A post belongs to one user
    {
        return $this->belongsTo(User::class);
    }
}

// Usage
$user = User::find(1);
foreach($user->posts as $post) {
    echo $post->title;
}

$post = Post::find(10);
echo $post->user->name;   // automatically gets the author

2. One to One

 bash

// User.php
public function profile()
{
    return $this->hasOne(Profile::class);
}

// Profile.php
public function user()
{
    return $this->belongsTo(User::class);
}

// Usage
$user->profile->bio;

3. Many to Many (Student Course)

 bash

// Migration (pivot table)
Schema::create('course_student', function (Blueprint $table) {
    $table->id();
    $table->foreignId('student_id')->constrained();
    $table->foreignId('course_id')->constrained();
    $table->integer('grade')->nullable();
    $table->timestamps();
});

// Student.php
public function courses()
{
    return $this->belongsToMany(Course::class)
                ->withPivot('grade')     // extra column
                ->withTimestamps();
}

// Usage
$student->courses()->attach($courseId, ['grade' => 85]);
$student->courses;         // all courses
foreach($student->courses as $course) {
    echo $course->pivot->grade;   // 85
}

4. Polymorphic (One Image for Post or Product)

 bash

// Migration
$table->morphs('imageable');   // creates imageable_id + imageable_type

// Image.php
public function imageable()
{
    return $this->morphTo();
}

// Post.php & Product.php
public function images()
{
    return $this->morphMany(Image::class, 'imageable');
}

// Usage
$post->images()->create(['url' => 'post1.jpg']);
$product->images()->create(['url' => 'shoe.jpg']);

4. Eager Loading (Very Important for Speed!)
Without eager loading → 1 + N queries (slow!)

 bash

foreach(User::all() as $user) {
    echo $user->posts->count();   // 100 users = 101 queries! Very bad
}

With eager loading → only 2 queries

 bash

$users = User::with('posts')->get();   // magic!
foreach($users as $user) {
    echo $user->posts->count();        // no extra query
}

Other useful ones:

 bash

User::with(['posts.comments'])->get();           // nested
User::withCount('posts')->get();                 // posts_count column
User::whereHas('posts', fn($q) => $q->where('published', 1))->get();

5. Quick Cheat Sheet (Save This!)

Relationship	Model A Code	Model B Code
One to Many	hasMany(Post::class)	belongsTo(User::class)
One to One	hasOne(Profile::class)	belongsTo(User::class)
Many to Many	belongsToMany(Course::class)	same on both sides
Polymorphic Many	morphMany(Image::class,’imageable’)	morphTo()

Final Thought

Best Practice (Bangladeshi Developers Follow This)

Always use with() when showing lists
Use withCount() for dashboard numbers
Use pivot table with withPivot() for grades, roles, etc.
Never write JOIN manually if relationship exists

Master these 6 relationships → you are 80% Laravel expert!Need full working project with all relationships?

Eloquent Relationships Explained Clearly (Laravel 12 – 2025 Version)

Final Thought

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