Rails include only selected columns from relation

Question

I will try to explain:

I have a table \'Product\' and a table \'Store\'. I\'m trying to get just the store name to show at the page, but ActiveRecord is returning me all

Answer 1

Just tried something similar to this on my project. This should work:

@products = Product.
  .order(id: :desc)
  .joins(:store)
  .select("products.id, products.store_id, stores.name")
  .limit(1)

Using joins as opposed to includes will make rails perform only one query, because joins doesn't eager-load the association.

Answer 2

You can do this via pluck and joins:

Product
  .order(id: :desc)
  .joins(:store)
  .pluck("products.id, products.store_id, stores.name")
  .limit(1)

You're going to get an array back that follows the order of the columns defined in pluck. I've written about pluck before if you're not familiar with it.

---

The other way is via a straight SQL query:

sql =<<-EOF
  SELECT products.id, products.store_id, stores.name
  FROM products INNER JOIN stores
    ON products.store_id = stores.id
  ORDER BY products.id DESC
  LIMIT 1
EOF
records = ActiveRecord::Base.connection.execute(sql)

#=> [{"id" => X, "store_id" => Y, "name" => Z, ... }]

Both options produce the same SQL statement, the just vary in how the results come out.