how to write active record query for selecting certain values in a column

Question

I have a dogs table which has age as an attribute. Dogs with ages between 1 year -12 years are in one column and dogs under 1 year have different column. I want to be abel to select dogs that are between 8 - 12 years in age and count them. This is my query but it only selects one dog with certain age.

@checkup = Dog.where(age: 8).count

Yes! Thank. it works. What if I had to select multiple string values in a column? — Ann
– Ann, Commented Oct 7, 2015 at 17:14
Not sure what you are asking,try asking another question explaining what you need. Meanwhile please accept my answer :) — Pavan
– Pavan, Commented Oct 7, 2015 at 17:20

max · Accepted Answer · 2015-10-08 18:38:12Z

1

As suggested by Pavan you could use a range to create a BETWEEN query.

@checkup = Dog.where(age: 8..12).count

But this approach is still flawed since you have to periodically update all your records as time passes!

Instead use a Date column to record the birthdate of the dogs.

rails g migration AddBirthdateToDogs birthdate:date
rake db:migrate

Then you can select the dogs by:

Dog.where(birthdate: 8.years.ago..12.years.ago

Or if you want to be fancy you can create a class method:

class Dog < ActiveRecord::Base
  # Select dogs by age
  # @param [Range, Fixnum] age
  # @return [ActiveRecord::Relation]
  # @example
  #   Dog.aged(0)
  #   Dog.aged(1..2) 
  def self.aged(age)
    if age.respond_to?(:map)
      age = age.map do |x|
        x.is_a?(Date)? x : x.years.ago  
      end 
      age = age.first..(age.last + 1.year)
    elsif age.respond_to?(:year)
      age = age.year.ago..(age + 1.year)
    end
    self.where(birthdate: ago)
  end
end

edited Oct 8, 2015 at 18:38

answered Oct 7, 2015 at 17:18

max

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2 Comments

max Over a year ago

You can also use a DateTime but I doubt you need that level of precision.

Ann Over a year ago

I am going over the fancy method you gave and I am learning more. Thanks.

Pavan · Accepted Answer · 2015-10-07 17:14:50Z

0

If I understood correctly, the below should work

@checkup = Dog.where(age: 8..12).count

which returns the count of the dogs which are between 8-12.

answered Oct 7, 2015 at 17:14

Pavan

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