如何在wordpress插件开发中手动获取帖子缩略图URL

Try This MySql Query

 SELECT
        p1.*,
        wm2.meta_value
    FROM 
        wp_posts p1
    LEFT JOIN 
        wp_postmeta wm1
        ON (
            wm1.post_id = p1.id 
            AND wm1.meta_value IS NOT NULL
            AND wm1.meta_key = "_thumbnail_id"              
        )
    LEFT JOIN 
        wp_postmeta wm2
        ON (
            wm1.meta_value = wm2.post_id
            AND wm2.meta_key = "_wp_attached_file"
            AND wm2.meta_value IS NOT NULL  
        )
    WHERE
        p1.post_status="publish" 
        AND p1.post_type="post"
    ORDER BY 
        p1.post_date DESC