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OtherJoins

Travis Code Climate Gem

Add obvious left_joins, outer_joins methods to ActiveRecord as plain way to join tables.

This version works with ActiveRecord (3.0.x - 4.2.x).

Introdution

Usually to join tables in Rails app you use something like this:

User.joins(:orders)
# SELECT "users".* FROM "users"
# INNER JOIN "orders" ON "orders"."user_id" = "users"."id"

Well, more living example. We want to get users with count of orders:

User.joins(:orders).group('users.name').count('orders.id')
# SELECT COUNT(orders.id) AS count_orders_id, users.name AS users_name
# FROM "users"
# INNER JOIN "orders" ON "orders"."user_id" = "users"."id"
# GROUP BY users.name
 => {"Nick"=>2, "Sandra"=>3}

But if we want to get all users and count of orders, even else orders empty. We call OUTER JOIN by handwriting SQL:

User.joins('LEFT OUTER JOIN orders ON orders.user_id = users.id').group('users.name').count('orders.id')
# SELECT COUNT(orders.id) AS count_orders_id, users.name AS users_name
# FROM "users"
# LEFT OUTER JOIN orders ON orders.user_id = users.id
# GROUP BY users.name
 => {"Juan"=>0, "Nick"=>2, "Sandra"=>3}

Not difficult, but it is bored and ungracefully. Instinctively we want to use left_join or outer_join etc.

Installation

Add this line to your application's Gemfile:

gem 'other_joins'

And then execute:

$ bundle

Or install it yourself as:

$ gem install other_joins

Usage

It's very easy and intuitive:

User.left_joins(:orders).group('users.name').count('orders.id')
# SELECT COUNT(DISTINCT orders.id) AS count_orders_id,
# users.name AS users_name
# FROM "users"
# LEFT OUTER JOIN "orders" ON "orders"."user_id" = "users"."id"
# GROUP BY users.name
 => {"Juan"=>0, "Nick"=>2, "Sandra"=>3}

Of course, you can use nested joins:

User.left_joins(orders: :shop)
# SELECT "users".* FROM "users"
# LEFT OUTER JOIN "orders" ON "orders"."user_id" = "users"."id"
# LEFT OUTER JOIN "shops" ON "shops"."id" = "orders"."shop_id"

Or array:

Order.left_joins(:user, :shop)
# SELECT "orders".* FROM "orders"
# LEFT OUTER JOIN "users" ON "users"."id" = "orders"."user_id"
# LEFT OUTER JOIN "shops" ON "shops"."id" = "orders"."shop_id"

And combine with standart joins method:

Order.left_joins(:shop).joins(:user)
# SELECT "orders".* FROM "orders"
# INNER JOIN "users" ON "users"."id" = "orders"."user_id"
# LEFT OUTER JOIN "shops" ON "shops"."id" = "orders"."shop_id"

You may use outer_joins method if it is more habitually for you. outer_joins is alias for left_joins If you want to take SQL-string, you shuold to use regular joins method.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ilp416/other_joins. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.