as is implemented

lib/arel/nodes/sum.rb

@@ -7,6 +7,16 @@ def initialize expr, aliaz = nil
         @expressions = expr
         @alias       = aliaz
       end
+
+      def as aliaz
+        self.alias = SqlLiteral.new(aliaz)
+        self
+      end
+
+      def to_sql
+        viz = Visitors::ToSql.new Table.engine
+        viz.accept self
+      end
     end
   end
 end