add_reference(table_name, *args) public

Adds a reference. The reference column is an integer by default, the :type option can be used to specify a different type. Optionally adds a _type column, if :polymorphic option is provided. #add_reference and #add_belongs_to are acceptable.

The options hash can include the following keys:


The reference column type. Defaults to :integer.


Add an appropriate index. Defaults to false. See #add_index for usage of this option.


Add an appropriate foreign key constraint. Defaults to false.


Whether an additional _type column should be added. Defaults to false.


Whether the column allows nulls. Defaults to true.

Create a user_id integer column
add_reference(:products, :user)
Create a user_id string column
add_reference(:products, :user, type: :string)
Create supplier_id, supplier_type columns and appropriate index
add_reference(:products, :supplier, polymorphic: true, index: true)
Create a supplier_id column with a unique index
add_reference(:products, :supplier, index: { unique: true })
Create a supplier_id column with a named index
add_reference(:products, :supplier, index: { name: "my_supplier_index" })
Create a supplier_id column and appropriate foreign key
add_reference(:products, :supplier, foreign_key: true)
Create a supplier_id column and a foreign key to the firms table
add_reference(:products, :supplier, foreign_key: {to_table: :firms})
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June 7, 2016
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foreign_key option

It is also possible to specify that add_foreign_key should be added to the schema:

add_reference(:products, :supplier, foreign_key: true)