Соединить несколько Select в один

У меня есть следующий код:

function get($min, $max)
{
    // Хосты и хиты
    $query = $this->db->query('
        SELECT COUNT(DISTINCT ip2long) AS hosts, COUNT(*) AS hits, `date` FROM tracking
        WHERE user_id = "' . $this->user_id . '" ' . ($this->sub_id != 0 ? 'AND sub_id = "' . $this->db->escape($this->sub_id) . '" ' : '') . ($this->offer_id != 0 ? 'AND offer_id = "' . $this->db->escape($this->offer_id) . '" ' : '') . 'AND time BETWEEN "' . strtotime($this->days_array[$min] . ' 00:00') . '" AND "' . strtotime($this->days_array[$max] . ' 23:59') . '"
        GROUP BY `date` ASC
    ');
    foreach ($query->result_array() as $k) {
        $this->data[$k['date']]['tracking']['hosts'] = $k['hosts'];
        $this->data[$k['date']]['tracking']['hits'] = $k['hits'];
    }
    // Конверсии
    $query = $this->db->query('
        SELECT COUNT(*) AS count, SUM(summa) AS summa, `date` FROM conversions
        WHERE user_id = "' . $this->user_id . '" ' . ($this->sub_id != 0 ? 'AND sub_id = "' . $this->db->escape($this->sub_id) . '" ' : '') . ($this->offer_id != 0 ? 'AND offer_id = "' . $this->db->escape($this->offer_id) . '" ' : '') . 'AND status = "1" AND time BETWEEN "' . strtotime($this->days_array[$min] . ' 00:00') . '" AND "' . strtotime($this->days_array[$max] . ' 23:59') . '"
        GROUP BY `date` ASC
    ');
    foreach ($query->result_array() as $k) {
        $this->data[$k['date']]['conversions']['count'] = $k['count'];
        $this->data[$k['date']]['conversions']['summa'] = $k['summa'];
    }
    // Регистрации
    $query = $this->db->query('
        SELECT COUNT(*) AS count, SUM(summa) AS summa, `date` FROM event_register
        WHERE user_id = "' . $this->user_id . '" ' . ($this->sub_id != 0 ? 'AND sub_id = "' . $this->db->escape($this->sub_id) . '" ' : '') . ($this->offer_id != 0 ? 'AND offer_id = "' . $this->db->escape($this->offer_id) . '" ' : '') . 'AND status = "1" AND time BETWEEN "' . strtotime($this->days_array[$min] . ' 00:00') . '" AND "' . strtotime($this->days_array[$max] . ' 23:59') . '"
        GROUP BY `date` ASC
    ');
    foreach ($query->result_array() as $k) {
        $this->data[$k['date']]['register']['count'] = $k['count'];
        $this->data[$k['date']]['register']['summa'] = $k['summa'];
    }
    // Покупки
    $query = $this->db->query('
        SELECT COUNT(*) AS count, SUM(summa) AS summa, `date` FROM event_buy
        WHERE user_id = "' . $this->user_id . '" ' . ($this->sub_id != 0 ? 'AND sub_id = "' . $this->db->escape($this->sub_id) . '" ' : '') . ($this->offer_id != 0 ? 'AND offer_id = "' . $this->db->escape($this->offer_id) . '" ' : '') . 'AND status = "1" AND time BETWEEN "' . strtotime($this->days_array[$min] . ' 00:00') . '" AND "' . strtotime($this->days_array[$max] . ' 23:59') . '"
        GROUP BY `date` ASC
    ');
    foreach ($query->result_array() as $k) {
        $this->data[$k['date']]['buy']['count'] = $k['count'];
        $this->data[$k['date']]['buy']['summa'] = $k['summa'];
    }
    // Заработок с рефералов
    $query = $this->db->query('
        SELECT SUM(summa) AS summa, `date` FROM referals
        WHERE user_id = "' . $this->user_id . '" AND time BETWEEN "' . strtotime($this->days_array[$min] . ' 00:00') . '" AND "' . strtotime($this->days_array[$max] . ' 23:59') . '"
        GROUP BY `date` ASC
    ');
    foreach ($query->result_array() as $k) {
        $this->data[$k['date']]['referals']['summa'] = $k['summa'];
    }
    $return = array();
    foreach ($this->data as $key => $k) {
        if (strtotime($key) >= strtotime($this->days_array[$min]) && strtotime($key) <= strtotime($this->days_array[$max])) {
            $return[$key] = $this->data[$key];
            $return[$key]['date'] = $key;
            // Трекинг
            $return[$key]['tracking']['hosts'] = (isset($return[$key]['tracking']['hosts']) ? $return[$key]['tracking']['hosts'] : 0);
            $return[$key]['tracking']['hits'] = (isset($return[$key]['tracking']['hits']) ? $return[$key]['tracking']['hits'] : 0);
            // Конверсии
            $return[$key]['conversions']['count'] = (isset($return[$key]['conversions']['count']) ? $return[$key]['conversions']['count'] : 0);
            $return[$key]['conversions']['summa'] = (isset($return[$key]['conversions']['summa']) ? $return[$key]['conversions']['summa'] : 0);
            // Регистрации
            $return[$key]['register']['count'] = (isset($return[$key]['register']['count']) ? $return[$key]['register']['count'] : 0);
            $return[$key]['register']['summa'] = (isset($return[$key]['register']['summa']) ? $return[$key]['register']['summa'] : 0);
            // Покупки
            $return[$key]['buy']['count'] = (isset($return[$key]['buy']['count']) ? $return[$key]['buy']['count'] : 0);
            $return[$key]['buy']['summa'] = (isset($return[$key]['buy']['summa']) ? $return[$key]['buy']['summa'] : 0);
            // Рефералы
            $return[$key]['referals']['summa'] = (isset($return[$key]['referals']['summa']) ? round($return[$key]['referals']['summa'], 2) : 0);
            // Менеджеры
            $return[$key]['managers']['summa'] = (isset($return[$key]['managers']['summa']) ? round($return[$key]['managers']['summa'], 2) : 0);
            // Общая сумма
            $return[$key]['summa'] = round($return[$key]['conversions']['summa'] + $return[$key]['register']['summa'] + $return[$key]['buy']['summa'] + $return[$key]['referals']['summa'] + $return[$key]['managers']['summa'], 2);
            // CTR
            $return[$key]['ctr'] = ((isset($return[$key]['buy']['count']) && isset($return[$key]['conversions']['count']) && $return[$key]['buy']['count'] > 0 && $return[$key]['conversions']['count'] > 0) ? round(($return[$key]['buy']['count'] / $return[$key]['conversions']['count']) * 100) : 0);
            // CR (Конверт)
            $return[$key]['cr'] = ((isset($return[$key]['tracking']['hosts']) && isset($return[$key]['conversions']['count']) && $return[$key]['tracking']['hosts'] > 0 && $return[$key]['conversions']['count'] > 0) ? round(($return[$key]['conversions']['count'] / $return[$key]['tracking']['hosts']) * 100) : 0);
            // Всего трекинг
            $this->total['tracking']['hosts'] += $return[$key]['tracking']['hosts'];
            $this->total['tracking']['hits'] += $return[$key]['tracking']['hits'];
            //Конверсии всего
            $this->total['conversions']['count'] += $return[$key]['conversions']['count'];
            // Регистрации всего
            $this->total['register']['count'] += $return[$key]['register']['count'];
            // Покупки всего
            $this->total['buy']['count'] += $return[$key]['buy']['count'];
            // Рефералы всего
            $this->total['referals']['summa'] += $return[$key]['referals']['summa'];
            // Общая сумма
            $this->total['summa'] += ($return[$key]['summa']);
        }
    }
    krsort($return);
    return $return;
}

Как видите, не самый оптимальный способ получения данных. Я бы хотел объединить эти селекты в один. При этом, я подумал о том, что нужно использовать FULL JOIN. Вот почему. Мне нужна таблица следующего вида

Количество строк в этой таблице будет равно количеству строк максимально большой выборки одного из селектов. Для примера возьму первый селект. Вот запрос:

SELECT  user_id, COUNT(DISTINCT ip2long) AS hosts, COUNT(*) AS hits, 
date FROM tracking
WHERE user_id = 8 AND time BETWEEN '1533884400' AND '1534402800'
GROUP BY tracking.date;

Вот результат:

Но мне хотелось бы что то типа такого:

Для этого я написал вот такой запрос:

SELECT * FROM
(SELECT  MIN(time) as min_time, user_id, COUNT(DISTINCT ip2long) AS 
  hosts, COUNT(*) AS hits, date FROM tracking
WHERE user_id = 8 AND time BETWEEN '1533884400' AND '1534402800'
GROUP BY tracking.date) as track
LEFT JOIN (
SELECT time, user_id, COUNT(*) AS count, SUM(summa) AS summa, date 
FROM conversions
WHERE user_id = 8 AND time BETWEEN '1533884400' AND '1534402800'
GROUP BY date, time) conv ON conv.user_id = track.user_id AND 
  track.min_time = conv.time
UNION ALL
SELECT * FROM
(SELECT MIN(time) as min_time, user_id, COUNT(DISTINCT ip2long) AS 
  hosts, COUNT(*) AS hits, date FROM tracking
WHERE user_id = 8 AND time BETWEEN '1533884400' AND '1534402800'
GROUP BY tracking.date) as track
RIGHT JOIN (
SELECT MIN(time) as min_time, user_id, COUNT(*) AS count, SUM(summa) 
  AS summa, date FROM conversions
WHERE user_id = 8 AND time BETWEEN '1533884400' AND '1534402800'
GROUP BY date, time) conv ON conv.user_id = track.user_id AND 
  track.min_time = conv.min_time
WHERE track.user_id is NULL  OR  track.user_id is NULL AND 
  track.min_time is NULL ;

Тут я пытаюсь реализовать full join (так как его нет в mysql). Вопрос следующий, это оптимальный способ или есть какой то способ лучше?