Add Returning With Sequel as a ruby til

Author: jbranchaud

README.md

@@ -231,6 +231,7 @@ _305 TILs and counting..._
 - [Rake Only Lists Tasks With Descriptions](ruby/rake-only-lists-tasks-with-descriptions.md)
 - [Replace The Current Process With An External Command](ruby/replace-the-current-process-with-an-external-command.md)
 - [Rendering ERB](ruby/rendering-erb.md)
+- [Returning With Sequel](ruby/returning-with-sequel.md)
 - [Safe Navigation Operator](ruby/safe-navigation-operator.md)
 - [Set RVM Default Ruby](ruby/set-rvm-default-ruby.md)
 - [Squeeze Out The Extra Space](ruby/squeeze-out-the-extra-space.md)

ruby/returning-with-sequel.md

@@ -0,0 +1,21 @@
+# Returning With Sequel
+
+The [`sequel`](https://github.com/jeremyevans/sequel) gem is a database
+toolkit that allows you to interact with most databases. PostgreSQL has
+support for composite primary keys, but `sequel`, which is supposed to return
+the `id` of newly inserted records, isn't sure what to return when faced
+with a composite primary key. You can get around this by telling `sequel`
+exactly what should be returned using the `#returning` method. For instance,
+get it to return just the `id` of the new record:
+
+```ruby
+DB[:floors].returning(:id).insert(hotel_id: 4, id: 1, ...)
+# [{id: 1}]
+```
+
+To get it to return both parts of composite key:
+
+```ruby
+DB[:floors].returning(:id, :hotel_id).insert(hotel_id: 4, id: 1, ...)
+# [{id: 1, hotel_id: 4}]
+```