app_user.rb

class AppUser < ActiveRecord::Base
	self.table_name = "AppUsers"
	self.primary_key = 'UserID'

	def self.authenticate(user_id, password)
    if user = AppUser.where(UserID: user_id, Password: password)
    	unless user.nil? || user.empty?
				return user
			end
		end
		return nil
  end
end

pages_controller.rb

 def login_attempt
	    authorized_user = AppUser.authenticate(params[:user_id],params[:user_password])
	    @user = authorized_user.column_names
	    if authorized_user
	      redirect_to(:action => 'main')
	    else
	      flash[:notice] = "Invalid Username or Password"
	      flash[:color]= "invalid"
	      render "login"	
	    end
	end

Rails Console

AppUser.authenticate('ADMIN', '')

  AppUser Load (0.9ms)  EXEC sp_executesql N'SELECT TOP (1) [AppUsers].* FROM [AppUsers] WHERE [AppUsers].[UserID] = N''ADMIN'' AND [AppUsers].[Password] = N'''' ORDER BY [AppUsers].[UserID] ASC'
 => #<AppUser UserID: "ADMIN", UserName: "Administrator", MenuGroup: "SYS_ADMIN", Password: "", DefaultStoreID: "1", FullRights: true, LastChanged: "2013-10-23 17:59:52", ChangedBy: "ADMIN", Email: "", Phone: "", Deleted: false, CashierID: "", HideCostPrice: false, WebLogin: false, CustomerID: "", DepID: "", NetworkID: "">