How to select only specific attributes from a model?

Question

I want to select only specific attributes from a model(id,name).

The SQL-command can be for example:

SELECT id,name,username FROM Users

Do you know how I can handle this?

Answer 1

There's a :select option on find methods. This allows you to do:

User.find(:all, :select => 'id, name, username')

The returned objects will be User instances with those attributes available.

Or if you really want just the values without wrapping them us as User instances. You can add a method to User to return them.

def self.get_ids_and_names
  self.connection.select_all("select id, name, username from users")
end

which will return an array of hashes mapping column name to the value for that row. E.g. [{'id' => 1, 'name' => 'user1', 'username' => 'username1'}, ... ]

Answer 2

You can also do

User.find(:all).map(&:id)

to get a list of the user ids if you are trying to get a list of user's ids or names