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Association

model "Author" {
}

model "Book" {
}

The Types of Associations​

  • belongs_to
  • has_one
  • has_many
  • has_many through
  • has_one through

belongs_to Association​

model "Book" {
  belongs_to "author" {}
}

add an optional database-level foreign key constraint

model "Book" {
  belongs_to "author" {
    foreign_key = true
  }
}

has_one Association​

model "Supplier" {
  has_one "account" {}
}

has_many Association​

model "Author" {
  has_many "books" {}
}

has_many through Association​

model "Physician" {
  has_many "appointments" {}
  has_many "patients" {
    through = "appointments"
  }
}

model "Appointment" {
  belongs_to "physician" {}
  belongs_to "patient" {}
}

model "Patient" {
  has_many "appointments" {}
  has_many "physicians" {
    through = "appointments"
  }
}

has_one through Association​