Question: In ZF1 it worked like this:

```
 $selectColumns = array(
   '*',
   'orders_total' => "(".$db->select()->from("orders", array("COUNT(*)"))->where("orders.parent_id=mytable.id").")",
 );
 $select = $db->select()->from('mytable', $selectColumns);

```

How to do this in the ZF2? Thanks.

Answer: 
Please try this.

```
$sql = new Sql($this->_adapter);
$mainSelect = $sql->select()->from('mytable');
$subQry = $sql->select()
        ->from('orders')
        ->columns(array('orderCount' => new \Zend\Db\Sql\Expression('COUNT(orders.id)')));
$mainSelect->columns(
        array(
            'id', 
            'orders_total' => new \Zend\Db\Sql\Expression('?', array($subQry)),
        )
);

$statement = $sql->prepareStatementForSqlObject($mainSelect);
$comments = $statement->execute();
$resultSet = new ResultSet();
$resultSet->initialize($comments);

return $resultSet->toArray();

```

Link: [ZF2 - subqueries](https://stackoverflow.com/questions/15742290/subquery-in-zend-framework2/15743270#15743270)
You can try restructuring your SQL to something like:

```
SELECT
    *,
    SUM(IF(O.parent_id IS NULL, 0, 1)) AS orders_total
FROM mytable
    LEFT JOIN orders O ON mytable.id = O.parent_id

```

Which you can represent using Zend Framework 2 as:

```
$select = new Select('mytable');
$select->columns(array(
    '*',
    'orders_total' => new Expression("SUM(IF(O.parent_id IS NULL, 0, 1))")
));
$select->join(array('O', 'orders'), 
              "mytable.id = O.parent_id",
              Select::JOIN_LEFT);   
$select->group(array('mytable.id'));

$result = $dbh->selectWith($select);

```

Assuming $dbh is your database adapter.