select_values(sql, name = nil) public

Returns an array of the values of the first column in a select: 

  select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
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April 9, 2009
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select_values returns Strings for MySQL

This method will return all values as strings from MySQL. It is easy to convert if required, for example, to integers:

select_values("SELECT id FROM companies LIMIT 3") => ['1','2','3']
select_values("SELECT id FROM companies LIMIT 3").collect(&:to_i) => [1,2,3]
June 17, 2011
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select_values returns Strings for postgreSQL

Will return strings too when using postgreSQL and gem pg (0.11.0).

June 20, 2011
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Typecasting return values

A better way to typecast the result array is to use AR’s typecasting capabilities. Example:

column = Company.columns_hash['id']
select_values("SELECT id FROM companies LIMIT 3").map do |value|
  column.type_cast(value)
end
August 25, 2015
0 thanks

Using Arel

You can also use Arel.

For example:

class ArticlePage < ActiveRecord::Base
  belongs_to :article
  scope :published, -> { where.not(published_at: nil) }
  scope :all_ready, -> { select("every(workflow_state = 'ready') AS is_ready") }
end

class Article < ActiveRecord::Base
  has_many :article_pages
  def all_ready?
    ActiveRecord::Base.select_values(article_pages.all_ready,published) = 't'
  end
end