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?
9 Answers
Pretty old question, but the rails 3 way would be:
User.pluck(:id)
Comments
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'}, ... ]
1 Comment
August Lilleaas
In Rails 3:
User.select("id,name,username")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
3 Comments
Ashitaka
I had been googling for this for a while. Thanks!
SG 86
I dont recommend it this way. Very slow
Blair Anderson
This is an answer, but its fairly slow.
User.find(:all) returns a complete collection of ActiveRecord objects for each item. then with ruby it maps over those objects and returns just the IDs. You've still got that collection waiting to be garbage collected. hopefully your IDs aren't being used for other memory intensive actions. User.pluck and User.select are more efficientWe can use select for symbol or string such as:
User.select("id, name, username")
or
User.select(:id, :name, :username)
Comments
You can also pass in an array, like so:
Model.all.select ['id', 'title']
Comments
In mongoid, that would be:
User.only(:name, :username).where(id: params[:id]).first
Comments
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)
Comments
actually for you only need write this
@user= User.select(:attributeN, :attributeN......., attributeN)
respond_to do |format|
format.json {
render json: @user
}
Comments
Just for those looking to get a single field
Client.select(:id) #The ids on an Active::Record collection Client.select(:id).pluck(:id) #the ids on an Array
