$select = $this->getTable()
    ->select()
    ->from(
        'property_stats',
        array(
            'stat_property_id',
            'month' => 'MONTH(`stat_date`)',
            'unique' => 'SUM(`stat_count_unique`)',
            'returning' => 'SUM(`stat_count_returning`)'
        )
    )
    ->joinLeft(
        'property',
        array('property_id = stat_property_id')
    )
    ->where('YEAR(`stat_date`) = YEAR(CURDATE())')
    ->group('stat_property_id')
    ->group('MONTH(`stat_date`)');