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

actually for you only need write this

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