我已经设法让wordpress对一个名为start_date 保存在Ymd 通过ACF插件在数据库中设置格式。

然而，在我的查询中，没有此字段的其他帖子类型是无序的，并且似乎总是位于包含元字段的所有帖子之后。

当前如何返回订单的示例：

贴子类型：右对齐日期：年月日新闻2020年9月19日新闻2019年3月12日新闻2018年6月5日出版2020年10月16日出版物2020年10月19日出版物2020年11月2日，这是我正在使用的pre\\u get\\u posts挂钩的摘录。

function orderby_fieldifexists($orderby) {
    return "mt1.post_id IS NOT NULL DESC, wp_postmeta.meta_value DESC, wp_posts.post_date DESC";
}
add_filter("posts_orderby", "orderby_fieldifexists", 10, 1);

$meta_query = [
    \'relation\' => \'OR\',
    \'start_date_value\' => [
        \'key\' => \'start_date\',
    ],
    \'start_date\' => [
        \'key\' => \'start_date\',
        \'compare\' => \'NOT EXISTS\'
    ]
];

$query->set(\'meta_query\', $meta_query);

有人知道为什么会发生这种情况吗？我已经被这个问题困扰了太长时间了，我在这里问，是否有人会发现我做错了什么。

下面是查询的SQL输出（其中包含来自wpml的几个翻译连接块）：

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
         LEFT JOIN wp_postmeta
                   ON ( wp_posts.ID = wp_postmeta.post_id )
         LEFT JOIN wp_postmeta AS mt1
                   ON (wp_posts.ID = mt1.post_id
                       AND mt1.meta_key = \'start_date\' )
         LEFT JOIN wp_icl_translations wpml_translations
                   ON wp_posts.ID = wpml_translations.element_id
                       AND wpml_translations.element_type = CONCAT(\'post_\', wp_posts.post_type)
WHERE 1=1
  AND (((wp_posts.post_title LIKE \'%Test%\')
    OR (wp_posts.post_excerpt LIKE \'%Test%\')
    OR (wp_posts.post_content LIKE \'%Test%\')))
  AND ( wp_postmeta.meta_key = \'start_date\'
    OR mt1.post_id IS NULL )
  AND wp_posts.post_type IN (\'post\', \'page\', \'news\', \'publication\', \'event\')
  AND (wp_posts.post_status = \'publish\'
    OR wp_posts.post_status = \'acf-disabled\'
    OR wp_posts.post_author = 1
           AND wp_posts.post_status = \'private\')
  AND ( ( ( wpml_translations.language_code = \'en\'
    OR ( wpml_translations.language_code = \'en\'
        AND wp_posts.post_type IN ( \'project\' )
        AND ( ( (
                    SELECT COUNT(element_id)
                    FROM wp_icl_translations
                    WHERE trid = wpml_translations.trid
                      AND language_code = \'en\' ) = 0 )
            OR ( (
                     SELECT COUNT(element_id)
                     FROM wp_icl_translations t2 JOIN wp_posts p
                                                      ON p.id = t2.element_id
                     WHERE t2.trid = wpml_translations.trid
                       AND t2.language_code = \'en\'
                       AND ( p.post_status = \'publish\'
                         OR p.post_type=\'attachment\'
                                 AND p.post_status = \'inherit\' ) ) = 0 ) ) ) )
    AND wp_posts.post_type IN (\'post\',\'page\',\'attachment\',\'wp_block\',\'news\',\'publication\',\'event\',\'project\' ) )
    OR wp_posts.post_type NOT IN (\'post\',\'page\',\'attachment\',\'wp_block\',\'news\',\'publication\',\'event\',\'project\') )
GROUP BY wp_posts.ID
ORDER BY mt1.post_id IS NOT NULL DESC, wp_postmeta.meta_value DESC, wp_posts.post_date DESC
LIMIT 0, 10

$meta_query = [
    \'relation\'         => \'OR\',
    \'start_date_value\' => [
        \'key\'  => \'start_date\',
        \'type\' => \'DATE\', // set the \'type\' to DATE
    ],
    \'start_date\'       => [
        \'key\'     => \'start_date\',
        \'compare\' => \'NOT EXISTS\',
    ],
];

$query->set( \'meta_query\', $meta_query );

// Use an array with the orderby.
$query->set( \'orderby\', [
    \'start_date_value\' => \'DESC\', // sorts by the meta start_date
    \'post_date\'        => \'DESC\', // then sorts by the post date
] );

---
**Query #1 - before sorting **

| Post Title    | start_date | Post Date              |
| ------------- | ---------- | ---------------------- |
| News 1        | 20200211   | March 12th, 4:00AM     |
| News 2        | 20200926   | September 19th, 5:36AM |
| News 3        |            | June 5th, 8:07PM       |
| Publication 1 | 20201021   | October 16th, 5:40PM   |
| Publication 2 | 20200211   | March 12th, 11:43AM    |

---
**Query #2 - after sorting by the meta start_date **

| Post Title    | start_date | Post Date              |
| ------------- | ---------- | ---------------------- |
| Publication 1 | 20201021   | October 16th, 5:40PM   |
| News 2        | 20200926   | September 19th, 5:36AM |
| News 1        | 20200211   | March 12th, 4:00AM     |
| Publication 2 | 20200211   | March 12th, 11:43AM    |
| News 3        |            | June 5th, 8:07PM       |

---
**Query #3 - after sorting by the meta start_date, AND THEN the post date **

| Post Title    | start_date | Post Date              |
| ------------- | ---------- | ---------------------- |
| Publication 1 | 20201021   | October 16th, 5:40PM   |
| News 2        | 20200926   | September 19th, 5:36AM |
| Publication 2 | 20200211   | March 12th, 11:43AM    |
| News 1        | 20200211   | March 12th, 4:00AM     |
| News 3        |            | June 5th, 8:07PM       |