mysql - Wordpress 按自定义字段查询顺序缺少帖子

Question

这是我当前的查询:

query_posts(array_merge(array('tag' => $pagetag,'meta_key'=>priority,'orderby' =>meta_value, 'order' =>'ASC','paged' => get_query_var('paged'))));

我的问题是查询仅向我显示具有我的“meta_key”值的帖子，这意味着“优先级”不为 NULL。 我怎样才能改进这个查询，以便它仍然按我的 meta_key 排序，但也会显示所有非 NULL 的帖子？

提前致谢!

Answer 1

问题是，只要您在条件中提到 meta_key，WordPress 就会将 INNER JOIN 添加到 wp_postmeta 表。解决该问题的一种方法是在 order by 子句上添加一个过滤器，如下所示:

function so_orderby_priority($original_orderby_statement) {
    global $wpdb;

    return "(SELECT $wpdb->postmeta.meta_value
               FROM $wpdb->postmeta
              WHERE $wpdb->posts.ID = $wpdb->postmeta.post_id
                AND $wpdb->postmeta.meta_key = 'priority') ASC";
}

add_filter('posts_orderby', 'so_orderby_priority');

query_posts(
    array(
        'tag' => $pagetag,
        'paged' => get_query_var('paged')
    )
);

remove_filter('posts_orderby', 'so_orderby_priority');

注意 MySQL 首先对 NULL 进行排序 - 如果您希望它们最后排序，请尝试这样的操作(假设您所有的优先级按字母顺序排列在 ZZZZZ 之前):

function so_orderby_priority($original_orderby_statement) {
    global $wpdb;

    return "IFNULL(
               (SELECT $wpdb->postmeta.meta_value
                  FROM $wpdb->postmeta
                 WHERE $wpdb->posts.ID = $wpdb->postmeta.post_id
                   AND $wpdb->postmeta.meta_key = 'priority'),
                'ZZZZZ') ASC";
}

编辑

这里有更多解释，假设您至少了解一点 SQL。

您的原始 query_posts 导致对数据库运行以下查询:

SELECT wp_posts.*
FROM   wp_posts
       INNER JOIN wp_term_relationships ON ( wp_posts.id = wp_term_relationships.object_id )
       INNER JOIN wp_postmeta ON ( wp_posts.id = wp_postmeta.post_id )
WHERE  1 = 1
       AND ( wp_term_relationships.term_taxonomy_id IN ( 3 ) )
       AND wp_posts.post_type = 'post'
       AND ( wp_posts.post_status = 'publish'
              OR wp_posts.post_status = 'private' )
       AND ( wp_postmeta.meta_key = 'priority' )
GROUP  BY wp_posts.id
ORDER  BY wp_postmeta.meta_value ASC
LIMIT  0, 10; 

那个 INNER JOIN wp_postmeta 是从你的结果中删除所有没有优先级的帖子的原因。

从您的query_posts 中删除meta_* 相关条件:

query_posts(
    array(
        'tag' => $pagetag,
        'paged' => get_query_var('paged')
    )
);

解决了那个问题，但是排序顺序还是错的。新的 SQL 是

SELECT wp_posts.*
FROM   wp_posts
       INNER JOIN wp_term_relationships ON ( wp_posts.id = wp_term_relationships.object_id )
WHERE  1 = 1
       AND ( wp_term_relationships.term_taxonomy_id IN ( 3 ) )
       AND wp_posts.post_type = 'post'
       AND ( wp_posts.post_status = 'publish'
              OR wp_posts.post_status = 'private' )
GROUP  BY wp_posts.id
ORDER  BY wp_posts.post_date DESC
LIMIT  0, 10; 

posts_orderby 过滤器允许我们更改ORDER BY 子句:wp_posts.post_date DESC 被过滤器返回的内容替换。最终的 SQL 变为:

SELECT wp_posts.*
FROM   wp_posts
       INNER JOIN wp_term_relationships ON ( wp_posts.id = wp_term_relationships.object_id )
WHERE  1 = 1
       AND ( wp_term_relationships.term_taxonomy_id IN ( 3 ) )
       AND wp_posts.post_type = 'post'
       AND ( wp_posts.post_status = 'publish'
              OR wp_posts.post_status = 'private' )
GROUP  BY wp_posts.id
ORDER  BY (SELECT wp_postmeta.meta_value
           FROM   wp_postmeta
           WHERE  wp_posts.id = wp_postmeta.post_id
                  AND wp_postmeta.meta_key = 'priority') ASC
LIMIT  0, 10 

哪个做你想要的。