这就是你要找的吗？

e.g. Remove all image attachments from a post

//get all image attachments
$attachments = get_children( 
                    array(
                        \'post_parent\'       => $post->ID,
                        \'post_mime_type\'    => \'image\',
                        \'post_type\'         => \'attachment\'
                    ) 
                );

//loop through the array
if( !empty( $attachments ) ){   
    foreach( $attachments as $attachment ){
        // Update the post into the database
          wp_update_post( array(
                    \'ID\' => $attachment->ID,
                    \'post_parent\' => 0
                )
            );
    }
}

Alternate method using $wpdb

//replace this with the above inside the foreach block;
global $wpdb;
$wpdb->query(
    "
    UPDATE $wpdb->posts 
    SET post_parent = 0
    WHERE ID = $attachment->id
        AND post_type = \'attachment\'
    "
);

从WordPress 4.2开始，此功能是内置的。单击Detach 媒体列表视图中的链接。

对于较旧版本，有一个插件可以执行相同的操作：https://wordpress.org/plugins/unattach/

Unattach是一个非常简单的插件，它允许从WordPress帖子、页面和其他内容类型中分离图像和其他媒体。