Relationship에 관련 동영상을 꼭 보세요.

https://opentutorials.org/module/4134/25270

https://sir.kr/so_app/401 에 나온

Ruby on Rails에 나와 있는 활성 레코드 관련 자료입니다.

Belongs to

Has One ==> 1:1 관계

Has Many ==> 1:N 관계

Has Many : Through  ==> N:M 관계

Has One : Through 

Has and Belongs to many

http://rubykr.github.io/rails_guides/association_basics.html

라라벨의 Eloquent ORM 의 Relationships입니다.

https://laravel.com/docs/5.8/eloquent-relationships

• Defining Relationships
  • One To One
  • One To Many
  • One To Many (Inverse)
  • Many To Many
  • Defining Custom Intermediate Table Models
  • Has One Through
  • Has Many Through
• Polymorphic Relationships
  • One To One
  • One To Many
  • Many To Many
  • Custom Polymorphic Types

이전 글도 참조하세요..

https://sir.kr/so_phpframework/367

https://sir.kr/so_phpframework/390

간단한것은 이해가 되지만 아직도 이해가 안되는 부분이 많네요..