* Define associations in Initializers

  You can define associations in Initializers. Arql will generate model classes based on the database schema when it starts, and then load the Initializer file.

  The Initializer file is a Ruby file, so you can define associations in it, for example:

  #+BEGIN_SRC ruby
    class Student
      has_many :courses, foreign_key: :student_id, class_name: 'Course'
      belongs_to :school, foreign_key: :school_id, class_name: 'School'

      has_and_belongs_to_many :teachers, join_table: 'students_teachers', foreign_key: :student_id, association_foreign_key: :teacher_id, class_name: 'Teacher'
    end

    class Course
      belongs_to :student, foreign_key: :student_id, class_name: 'Student'
    end

    class School
      has_many :students, foreign_key: :school_id, class_name: 'Student'
    end

    class Teacher
      has_and_belongs_to_many :students, join_table: 'students_teachers', foreign_key: :teacher_id, association_foreign_key: :student_id, class_name: 'Student'
    end
  #+END_SRC

  1. =has_one= indicates that this table is the owner of a one-to-one relationship
  2. =belongs_to= indicates that this table is the dependent side of a one-to-many or one-to-one relationship
  3. =has_and_belongs_to_many= indicates that this table is one of the many-to-many relationships
  4. =class_name= indicates the Model class name of the corresponding relationship (the Model class name is actually the CamelCase form of the table name)
  5. =foreign_key= indicates the name of the association field on the dependent side of the association
  6. =primary_key= indicates the name of the association field on the owner side of the association
  7. =join_table= in many-to-many relationships, indicates the name of the intermediate table that associates the two tables
  8. =association_foreign_key= in many-to-many relationships, indicates the association field name of the other Model in the intermediate table

  You can refer to: https://guides.rubyonrails.org/association_basics.html