How to map irregular database tables with rails models

Rails specifies standard conventions while creating models, controllers, migrations ( database tables ).

Conventions for creating database tables

1. Table name should be plural

2. id field must be primary_key for table.

3. foreign_key  must be like <model_name>_id i.e. post_id, site_id

Conventions for creating models & Controllers
1. Model name must be singular and controller name should be plural.
Although rails have some standard defined, sometimes it becomes quite necessary to map rails models with non- standard database tables.
1. Table mapping

class Review < ActiveRecord::Base
  # Here comments is name of database table
  set_table_name :comments
end

2. Set primary key ( other than rails standar ‘id’ primary_key )

class Review < ActiveRecord::Base
  # It assumes "reviews" as table in database
  # Below line indicates reviews table contains column_name "reviewId" which is a primary_key
  set_primary_key :reviewId
end

3. Foreign key association


class Review < ActiveRecord::Base
  # Below line indicates reviews table contains column_name 'RatingId' which is foreign_key to primary_key
  # of 'ratings' table.
  # It can be applied to any associan type [ has_one, has_many, belongs_to, has_many_through ]
  belongs_to :rating, :class_name => "SiteUser", :foreign_key => "RatingId"
end

class Review < ActiveRecord::Base
  # Below line indicates reviews table contains column_name 'UserId' which is foreign_key to primary_key
  # of model with class_name 'SiteUser'
  belongs_to :user, :class_name => 'SiteUser', :foreign_key: => 'UserId'
end