public function orderAsc($field, $overwrite = false)
{
if ($overwrite) {
$this->_parts['order'] = null;
}
if (!$field) {
return $this;
}
if (!$this->_parts['order']) {
$this->_parts['order'] = new OrderByExpression();
}
$this->_parts['order']->add(new OrderClauseExpression($field, 'ASC'));
return $this;
}