In a service or controller, you can add a dependency injection for the dataSource bean and use groovy.sql.Sql or JDBC directly if you're a masochist. :) by Burt Beckwith [http://stackoverflow.com/questions/4600729/grails-query-not-using-gorm/4600991#4600991]

JdbcService

import groovy.sql.Sql

class DataService {

   def dataSource

   void runQuery(...) {
      def sql = new Sql(dataSource)
      sql.eachRow('select * from foo') { row ->
         ...
      }
   }
}