我正在为一个具有事件列表功能的站点编写一对查询。活动可以在一个日期或多个日期（多天）进行。所有事件在自定义字段中都有一个值event_date. 多日活动也有end_date 价值

单日事件应在“即将到来的事件”列表（第一次查询）中，直到其结束event_date, 多日活动应持续到活动结束end_date. 一旦他们不再在即将到来的列表中，他们应该移到“过去的事件”列表（新查询，同一页）。

即将进行的查询工作正常。多日活动在其event_date 和end_date 值：

$now     = date(\'Ymd\', strtotime("now"));
$future  = date(\'Ymd\', strtotime("+24 months"));
$uc_args = array(
    \'post_type\'  => \'event\',
    \'meta_query\' => array(
        \'relation\' => \'OR\',
        // check post has end_date and it is between $now and $future
        array(
            \'key\'     => \'end_date\',
            \'compare\' => \'BETWEEN\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => array($now, $future),
        ),
        // if no end date check event_date is between $now and $future
        array(
            \'key\'     => \'event_date\',
            \'compare\' => \'BETWEEN\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => array($now, $future),
        ),
    ),
    \'meta_key\' => \'event_date\',
    \'orderby\'  => \'meta_value\',
    \'order\'    => \'ASC\',
    \'nopaging\' => true,
);

过去的查询是以完全相同的方式构造的，但多日事件在其event–date 已经过去了，即使他们有end_date 值：

$past    = date(\'Ymd\', strtotime("-999 months"));
$now     = date(\'Ymd\', strtotime("now"));
$uc_args = array(
    \'post_type\'  => \'event\',
    \'meta_query\' => array(
        \'relation\'  => \'OR\',
        // check post has end_date and it is between $past and $now
        array(
            \'key\'     => \'end_date\',
            \'compare\' => \'BETWEEN\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => array($past, $now),
        ),
        // if no end date check event_date is between $past and $now
        array(
            \'key\'     => \'event_date\',
            \'compare\' => \'BETWEEN\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => array($past, $now),
        ),
    ),
    \'meta_key\'       => \'event_date\',
    \'orderby\'        => \'meta_value\',
    \'order\'          => \'DESC\',
    \'nopaging\'       => false,
    \'posts_per_page\' => \'8\',
);

我可以看到OR关系如何包含所有满足任一条件的帖子，但在第一个查询中它没有这样做。据我所知，没有其他关系，但这就是我在这里的目标。

为什么这适用于即将举行的活动，但不适用于过去的活动？

        array(
            \'key\'     => \'end_date\',
            \'compare\' => \'BETWEEN\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => array($past, $now),
        ),

        array(
            \'key\'     => \'end_date\',
            \'compare\' => \'<\',
            \'type\'    => \'NUMERIC\',
            \'value\'   => $now,
        ),