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 h

Answer 1

Pretty old question, but the rails 3 way would be:

User.pluck(:id)

Answer 2

SQL

SELECT id,name,username FROM Users

RUBY

User.select(:id, :name, :username)

with condition, you can write like: User.select(:id, :name, :username).find_by(:age 22)

Answer 3

actually for you only need write this

@user= User.select(:attributeN, :attributeN......., attributeN)
respond_to do |format|
  format.json {
    render json: @user
  }

Answer 4

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 5

We can use select for symbol or string such as:

User.select("id, name, username")

or

User.select(:id, :name, :username)

Answer 6

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