MySQL，如何使用不同的ID从两个表中获取一次又一次？

I have two tables and post.

Tables are paper, subject, some post content saved and opened in subject page.

Here issue is paper ID is Common but Subject ID changes for multiple posts.

$stmt = mysql_query("SELECT *  FROM tut_blog_posts WHERE paper_name='".$results_paper["id"]."' AND subject_name='".$results_subject["id"]."' ORDER BY postID DESC");

Sometime data works and other times the same paper ID and Subject ID don't work.

How to fix this?