title: How to resolve No data type for node error in hibernate
body: <p>I have table  vehicle ,i have written query as below</p>
  
  <p>Vehicle.executeQuery("select audio_system from Vehicle ")
  but i am getting an error </p>
  
  <blockquote>
    <p>ERROR groovy.grails.web.errors.GrailsExceptionResolver ### No data type for node: org.hibernate.hql.ast.tree.IdentNode 
     -[IDENT] IdentNode: 'audio_system' {originalText=audio_system}</p>
    
    <p>java.lang.IllegalStateException: No data type for node: org.hibernate.hql.ast.tree.IdentNode 
     -[IDENT] IdentNode: 'audio_system' {originalText=audio_system}</p>
  </blockquote>
  
  <p>Source code of vehicle class as follows</p>
  
  <pre><code>class Vehicle {
  
  
      String vehicleSticker
      String regNumber //plate
      String chasisNumber
      String engineNumber
      Integer yearOfManufacture
      Date purchasedOn
  
      Boolean audioSystem
      Boolean videoSystem
      Boolean mobileCharger
      Boolean laptopCharger
  
      //Vehicle compliance
      Date pucExpiry
      Date pucTestingOn
      Date taxTokenIssueDate
      Date taxTokenExpiryDate
      Date insuranceIssueDate
      Date insuranceExpiryDate
      Date permitIssueDate
      Date permitExpiryDate
      Date fitnessCertificateIssueDate
      Date fitnessCertificateExpiryDate
      Double odoReadingWhenServiceDone
      Double dueOddReading
  
      VendorRole vendor
  
      VehicleType vehicleType
      //RegistrationCertificate registrationCertificate
  
      static mapping = {
          //registrationCertificate(cascade:'all')
  
      }
  
      static constraints = {
          yearOfManufacture(nullable:true)
          regNumber(nullable:false,unique: true)
          chasisNumber(blank:true)
          engineNumber(blank:true)
          purchasedOn(nullable:true)
          taxTokenIssueDate(nullable:true)
          taxTokenExpiryDate(nullable:true)
  
          insuranceIssueDate(nullable:true)
          insuranceExpiryDate(nullable:true)
          permitIssueDate(nullable:true)
          permitExpiryDate(nullable:true)
          fitnessCertificateIssueDate(nullable:true)
          fitnessCertificateExpiryDate(nullable:true)
          odoReadingWhenServiceDone(nullable:true)
  
          dueOddReading(nullable:true)
          pucExpiry(nullable:true)
          pucTestingOn(nullable:true)
  
          vendor(nullable:true)
  
  
      }
  
      public String toString() {
          "${vehicleSticker} ${regNumber?'| '+ regNumber:''}"
      }
  </code></pre>