Find by sql in ActiveRecord

challenge.rb

def self.open_for_participant(contact_id, group_id = nil)
    
    find_by_sql(<<-SQL)
      SELECT challenges.* FROM challenges
      LEFT OUTER JOIN challenge_participants ON challenge_participants.challenge_id = challenges.id
        AND challenge_participants.contact_id = #{contact_id}
      WHERE (EXISTS (
      	SELECT 1 FROM group_challenges
      	JOIN group_contacts ON group_challenges.group_id = group_contacts.group_id
      	#{"JOIN groups on group_challenges.group_id = groups.id" if group_id}
      	WHERE group_contacts.contact_id = #{contact_id}
        	AND group_challenges.challenge_id = challenges.id
        	AND group_challenges.restrict_participants = TRUE
        	#{"AND groups.id = #{group_id}" if group_id}
      ) 
      #{"OR open_to_all = TRUE" unless group_id}) 
      AND challenge_participants.id is NULL
      AND (challenges.due_date IS NULL OR challenges.due_date >= '#{Time.now}')
      AND challenges.state = 'active'
      AND challenges.published = TRUE
    SQL
  end