MySQL子查询返回多个结果

Question

有人能找到一种使该代码即使在MySQL子查询返回多个结果的情况下也能起作用的方法吗？ 当用户没有与他有关的事件时，或者当用户有一个与他有关的事件时，它工作正常，但是当用户与一个以上事件有关时，子查询返回多个结果，并且代码没有任何结果跟...共事。

$stmt = $db->prepare("SELECT * FROM events WHERE
                  id_events = ( SELECT id_events FROM relationship_events WHERE id_user = ?)");
$stmt->bindParam(1, $idUser);
$stmt->execute();

$rawTimeStamps = $stmt->fetchAll(PDO::FETCH_ASSOC);
$cleanDateArray = array();

foreach ($rawTimeStamps as $t) {
$rawDate = $t['start'];
$rawDate = getdate($rawDate);
$cleanDate = mktime(0,0,0,$rawDate['mon'],$rawDate['mday'],$rawDate['year']);
$cleanDateArray[] = $cleanDate;
}

for($list_day = 1; $list_day <= $days_in_month; $list_day++):

$calendar.= '<td class="calendar-day">';
    $timestamp = mktime(0,0,0,$month,$list_day,$year);
    if (!empty($cleanDateArray) && in_array($timestamp, $cleanDateArray)) {

    $date = getdate($timestamp);
    $time_start = mktime(0,0,0,$date['mon'],$date['mday'],$date['year']);
    $time_end = mktime(23,59,59,$date['mon'],$date['mday'],$date['year']);
    $stmt = $db->prepare('SELECT title FROM events WHERE start BETWEEN ? AND ?');
    $stmt->bindParam(1,$time_start,PDO::PARAM_INT);
    $stmt->bindParam(2,$time_end,PDO::PARAM_INT);
    $stmt->execute();
    $events = $stmt->fetch(PDO::FETCH_ASSOC);

    $calendar.= '<div class="day-number day-number-event"><a href="#">'.$list_day.'</a></div><p>'.$events["title"].'</p>';
    } else {
    $calendar.= '<div class="day-number day-number-noevent">'.$list_day.'</div><div id="calendar-events"></div>';
    }

Answer 1

查询应该是SELECT * FROM events WHERE id_events IN ( SELECT id_events FROM relationship_events WHERE id_user = ?) 。

Answer 2

有两个可能的答案，具体取决于您希望它如何工作。

如果只希望一个事件，无论用户是否有1个或多个事件，都可以在子查询中添加LIMIT 1 ：

SELECT * FROM events
WHERE id_events = (
    SELECT id_events FROM relationship_events WHERE id_user = ? LIMIT 1
)

另一方面，如果要将所有事件分配给用户，则可以使用IN子句：

SELECT * FROM events
WHERE id_events IN (
    SELECT id_events FROM relationship_events WHERE id_user = ?
)

如果未将用户分配给任何事件，则这两个选项也应正常工作。