Can't get subquery to work

I need to perform this query:

SELECT a, COUNT(a) FROM
(SELECT user_id, a FROM database GROUP BY user_id) as users
WHERE a IS NOT NULL
GROUP BY a

Can't find any way to do this kind of subquery in Phalcon. Any help would be much appreciated.

Resorted to raw sql.

        $sql = "
            SELECT a, COUNT(a) FROM
            (SELECT user_id, a FROM table GROUP BY user_id) as users
            WHERE a IS NOT NULL
            GROUP BY a
        ";

        $table = new Table();

        return new \Phalcon\Mvc\Model\Resultset\Simple(
            null,
            $table,
            $table->getReadConnection()->query($sql)
        );

Subqueries are not yet supported in QueryBuilder yet. Raw sql is the way to go.

Create a view then you'll be able to use it as a model

There are supported, just not in this form. They are supported like:

SELECT someColumn, (SELECT otherColumn FROM OtherModel) as otherColumn FROM users