Add row to SQL array

What about something like this ?

$custom_row = array(array('race_id' => '1', 'race_name' => '2', 'race_date' => '3'));

$races = $wpdb->get_results("
      select r.race_name
            ,r.race_id
            ,date_format(r.race_date,'%c.%d.%Y') race_date
        from race_calendar r
       order by r.race_date;
      ", ARRAY_N);
$merged_arr = array_merge($custom_row, $races);
foreach ( $merged_arr as $race ) {
  echo $race['race_id'] . ',' . $race['race_name'] . ',' . $race['race_date'];
}

UPDATE

$custom_row = array(array('1', '2', '3'));

$races = $wpdb->get_results("
      select r.race_name
            ,r.race_id
            ,date_format(r.race_date,'%c.%d.%Y') race_date
        from race_calendar r
       order by r.race_date;
      ", ARRAY_N);
$merged_arr = array_merge($custom_row, $races);
foreach ( $merged_arr as $race ) {
  echo $race['0'] . ',' . $race['1'] . ',' . $race['2'];
}