Order By Multiple Meta Fields

    $args = array(
        'posts_per_page' => -1,
        'post_type' => 'cpt_program',
        'meta_query' => array(
            'relation' => 'OR',
            'ongoing' => array(
                'key'     => 'prog_ongoing',
                'value'   => 1
            ),
            'start_date' => array(
                array(
                    'key' => 'prog_date_start',
                    'value'   => date('Ymd'),
                    'type'    => 'numeric',
                    'compare' => '>='
                )
            )
        ),
        'orderby' => 'start_date ongoing',
        'order'   => 'ASC',
    );

Returns this:

Date: (1)
Date: 04/10/15 (1)
Date: (1)
Date: (1)
Date: (1)
Date: 04/21/15 (1)
Date: 06/11/15 (1)
Date: (1)
Date: 06/11/15 (1)
Date: 06/23/15 ()
Date: 06/30/15 ()

I'm not sure what determines the order when the prog_date_start is not set?

===================

Results I'd like:

Date: 06/23/15 () // Not prog_ongoing comes first, ordered by prog_date_start
Date: 06/30/15 ()
Date: 04/10/15 (1) // prog_ongoing ordered by prog_date_start (those with set prog_date_start first)
Date: 04/21/15 (1)
Date: 06/11/15 (1)
Date: (1) (all prog_ongoing without set prog_date_start at the end)
""

====================

If I use the following I get real close.

$meta_key1 = 'prog_ongoing';
$meta_key2 = 'prog_date_start';
$start_date = date('Ymd');

$postids = $wpdb->get_col( $wpdb->prepare(
    "
    SELECT      DISTINCT key1.post_id
    FROM        $wpdb->postmeta key1
    INNER JOIN  $wpdb->postmeta key2
                ON key2.post_id = key1.post_id
                AND key2.meta_key = %s
    WHERE       key1.meta_key = %s
                AND key1.meta_value is TRUE
                OR key2.meta_value >= %d
    ORDER BY    COALESCE(NULLIF(key1.meta_value, 0), 0) DESC, COALESCE(NULLIF(key2.meta_value, ''), $start_date) ASC, key2.meta_value ASC
    ",
    $meta_key2,
    $meta_key1,
    $start_date
) );

Returns this:

Date: 06/30/15 () // These top two are the problem. They don't order by prog_date_start. prog_ongoing equals 0 with these two.
Date: 06/23/15 ()
Date: 04/10/15 (1)
Date: 04/21/15 (1)
Date: 06/11/15 (1)
Date: (1) (all prog_ongoing without set date at the end)