在php中使用union订购

Question

I want to use order by statement that provide me result of top.

$sql_ins = "select user_first_name, user_last_name, user_id from user 
            INNER JOIN xyz on user_id=s_id 
            where (s_id='".$_SESSION['user']."' OR r_id='".$_SESSION['user']."')
              AND user_id!='".$_SESSION['user']."' group by user_id

            UNION

            SELECT user_first_name, user_last_name, user_id from user 
            INNER JOIN xyz on user_id=r_id 
            WHERE (r_id='".$_SESSION['user']."' OR s_id='".$_SESSION['user']."')
              AND user_id!='".$_SESSION['user']."' 

            GROUP BY user_id";

I want to get output by order by id desc but the output is an error.

Answer 1

Use this query it's worked for me....

SELECT * 
FROM (SELECT content_update.id as id, 
             content_update.course_id as course_id, 
             content_update.status as status, 
             content_update.title as title, 
             content_update.img_src as img, 
             content_update.entry_date as entry_date 
      FROM content_update 

      UNION ALL 

      SELECT video_update.id as id, 
             video_update.course_id as course_id, 
             video_update.status as status,
             video_update.title as title, 
             video_update.video_link as img, 
             video_update.entry_date as entry_date 
      FROM video_update ) results 

ORDER BY entry_date DESC