Foreign Key Migrations is a plugin that automatically generates foreign-key constraints when creating tables. It uses SQL-92 syntax and as such should be compatible with most databases that support foreign-key constraints.

In the simplest case, the plugin assumes that if you have a column named customer_id that you want a foreign-key constraint generated that references the id column in the customers table:

create_table :orders do |t|
  t.column :customer_id, :integer, :null => false
  ...
end

If you have multiple columns referencing a table or for whatever reason, your column name isn’t the same as the referenced table name, you can use the :references option:

create_table :orders do |t|
  t.column :ordered_by_id, :integer, :null => false, :references => :customers
  ...
end

If you have a column with a name ending in _id for which you do not wish a foreign-key to be generated, you can use :references => nil:

create_table :orders do |t|
  t.column :external_id, :integer, :null => false, :references => nil
  ...
end

You also have the option of specifying what to do on delete/update using :on_delete/:on_update, respectively to one of: :cascade; :restrict; and :set_null:

create_table :orders do |t|
  t.column :customer_id, :integer, :on_delete => :set_null, :on_update => :cascade
  ...
end

The plugin fully supports and understands the following active-record configuration properties:

• config.active_record.pluralize_table_names
• config.active_record.table_name_prefix
• config.active_record.table_name_suffix

=== Dependencies

• RedHill on Rails Core (redhillonrails_core).

=== See Also

• Foreign Key Associations (foreign_key_associations).