I replied to a similar question in another thread: Ecto preload for tag has_many tags
To summarise, asking “How to do this in ecto” is the wrong question. The right question is “How to do this in SQL”. Ecto, differently from ORMs (and that’s probably the important difference, not the fact that elixir doesn’t have objects), keeps close to the semantics of the underlying data storage and does not try to abstract it. This means that to use Ecto efficiently, one should understand the database.
