Escapes an alias name string.
Force all alias names to be strictly alphanumeric-plus-underscore. In contrast to DatabaseConnection::escapeField() / DatabaseConnection::escapeTable(), this doesn't allow the period (".") because that is not allowed in aliases.
The sanitized field name string.
public function escapeAlias($field) {
return preg_replace('/[^A-Za-z0-9_]+/', '', $field);
}