public function assembleField(FieldExpression $field)
 {
     if ($field->hasTable()) {
         return $this->assembleTableExpression($field->getTable()) . '.' . $this->escapeField($field->getField());
     } else {
         return $this->escapeField($field->getField());
     }
 }
 public function assembleFieldExpression(FieldExpression $expr)
 {
     return ($expr->hasTable() ? $this->assembleSegment($expr->getTable()) . '.' : '') . $this->escapeField($expr->getField());
 }