---
title: "Rails 5 allows UUID as column type in create_join_table"
description:
  "Rails 5 started supporting UUID as a column type in create_join_table."
canonical_url: "https://www.bigbinary.com/blog/rails-5-create-join-table-with-uuid"
markdown_url: "https://www.bigbinary.com/blog/rails-5-create-join-table-with-uuid.md"
---

# Rails 5 allows UUID as column type in create_join_table

Rails 5 started supporting UUID as a column type in create_join_table.

- Author: Hitesh Rawal
- Published: June 16, 2016
- Categories: Rails 5, Rails

In Rails 4.x
[create_join_table](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-create_join_table)
allows us to create new join table with name given in first two arguments.

```ruby

class CreateJoinTableCustomerProduct < ActiveRecord::Migration
  def change
    create_join_table(:customers, :products)
  end
end

```

It will create new join table `customer_products` with columns `customer_id` and
`product_id`. We can also use block with `create_join_table`.

```ruby

class CreateJoinTableCustomerProduct < ActiveRecord::Migration
  def change
    create_join_table :customers, :products do |t|
      t.index :customer_id
      t.index :product_id
    end
  end
end

```

However `create_join_table` won't allows us to define the column type. It will
always create column of `integer` type. Because Rails 4.x ,by default, supports
primary key column type as an auto increment `integer`.

If we wish to set `uuid` as a column type, then `create_join_table` won't work.
In such case we have to create join table manually using `create_table`.

Here is an example with Rails 4.x.

```ruby

class CreateJoinTableCustomerProduct < ActiveRecord::Migration
  def change
    create_table :customer_products do |t|
      t.uuid :customer_id
      t.uuid :product_id
    end
  end
end

```

## Rails 5 allows to have UUID as column type in join table

Rails 5 has started supporting UUID as a column type for primary key, so
`create_join_table` should also support UUID as a column type instead of only
integers. Hence now Rails 5 allows us to use
[UUID as a column type with create_join_table](https://github.com/rails/rails/pull/24221).

Here is revised example.

```ruby

class CreateJoinTableCustomerProduct < ActiveRecord::Migration[5.0]
  def change
    create_join_table(:customers, :products, column_options: {type: :uuid})
  end
end

```

## Links

- [Human page](https://www.bigbinary.com/blog/rails-5-create-join-table-with-uuid)