Laravel Eloquent ORM (Object-Relational Mapper) 관계

One-to-One Relationship:

users
id – integer
name – string

phones
id – integer
user_id – integer

In the User model:

public function phone()
{
   return $this->hasOne(Phone::class);
}

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In the Phone model:

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

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One-to-Many Relationship:

posts
id – integer
name – string

comments
id – integer
post_id – integer

In the Post model:

public function comments()
{
     return $this->hasMany(Comment::class);
}

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In the Comment model:

public function post()
{
        return $this->belongsTo(Post::class);
}

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Many-to-many Relationship:

users
id – integer
name – string

roles
id – integer
name – string

role_user (Pivot table)
user_id – integer
role_id – integer

In User model

public function roles()
{
    return $this->belongsToMany(Role::class, 'role_user');
}

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In Role model:

public function users()
{
     return $this->belongsToMany(User::class, 'role_user');
}

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Important Note:

• The pivot table is always singular; if you give it another name, make it plural.
• The name of the pivot table is ordered alphabetically.
• If the pivot table has more than two foreign keys, you use it as a normal table and create a model for it.

One-to-One (Polymorphic):
posts
id – integer
name – string

users
id – integer
name – string

images
id – integer
url – string
imageable_id – integer
imageable_type – string

In the Image model

public function imageable(): MorphTo
{
     return $this->morphTo();
}

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In the User model:

public function image(): MorphOne
{
    return $this->morphOne(Image::class, 'imageable');
}

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In the Post model:

public function image(): MorphOne
{
    return $this->morphOne(Image::class, 'imageable');
}

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One-to-Many (Polymorphic):
posts
id – integer
title – string
body – text

videos
id – integer
title – string
url – string

comments
id – integer
body – text
commentable_id – integer
commentable_type – string

In the Comment model:

public function commentable(): MorphTo
{
      return $this->morphTo();
}

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In the Video model:

public function comments(): MorphOne
{
     return $this->morphMany(Comment::class, 'commentable');
}

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In the Post model:

public function comments(): MorphOne
{
    return $this->morphMany(Comment::class, 'commentable');
}

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Many-to-Many (Polymorphic):
posts
id – integer
name – string

videos
id – integer
name – string

tags
id – integer
name – string

taggables
tag_id – integer
taggable_id – integer
taggable_type – string

In the Tag model:

public function videos(): MorphToMany
{
      return $this->morphedByMany(Video::class, 'taggable');
}

public function posts(): MorphToMany
{
     return $this->morphedByMany(Post::class, 'taggable');
}

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In the Video model:

public function tags(): MorphToMany
{
     return $this->morphToMany(Tag::class, 'taggable');
}

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In the Post model:

public function tags(): MorphToMany
{
     return $this->morphToMany(Tag::class, 'taggable');
}

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Has One Through Relationship:
The “has-one-through” relationship defines a one-to-one relationship with another model.
mechanics
id – integer
name – string

cars
id – integer
model – string
mechanic_id – integer

owners
id – integer
name – string
car_id – integer

In the Mechanic Model:

public function carOwner(): HasOneThrough
{
   return $this->hasOneThrough(Owner::class, Car::class);
}

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Has Many Through Relationship:
The “has-many-through” relationship defines a many-to-many relationship with another model.
projects
id – integer
name – string

environments
id – integer
project_id – integer
name – string

deployments
id – integer
environment_id – integer
commit_hash – string

In the Project Model:

public function deployments(): HasManyThrough
{
    return $this->hasManyThrough(Deployment::class, Environment::class);
}

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