public function aggregation($function)
{
$aggregation = & $this->refTable->aggregation[$function . implode('', $this->where) . implode('', $this->conditions)];
if ($aggregation === NULL) {
$aggregation = array();
$selection = new NTableSelection($this->name, $this->connection);
$selection->where = $this->where;
$selection->parameters = $this->parameters;
$selection->conditions = $this->conditions;
$selection->select($function);
$selection->select("{$this->name}.{$this->column}");
$selection->group("{$this->name}.{$this->column}");
foreach ($selection as $row) {
$aggregation[$row[$this->column]] = $row;
}
}
if (isset($aggregation[$this->active])) {
foreach ($aggregation[$this->active] as $val) {
return $val;
}
}
}