private boolean validateColumnsRecurse(TExpression condition, TJoinList joins) {
   if (condition.getLeftOperand().getLeftOperand() == null
       && condition.getRightOperand().getLeftOperand() == null) {
     return validateColumns(condition.getLeftOperand().toString(), joins)
         .equals(validateColumns(condition.getRightOperand().toString(), joins));
   } else {
     return (validateColumnsRecurse(condition.getLeftOperand(), joins)
         && validateColumnsRecurse(condition.getRightOperand(), joins));
   }
 }