recemet comments SQL

when i try:

$request = “SELECT ID, comment_ID, comment_content, comment_author, comment_author_url, post_title
FROM
$wpdb->comments AS cm,
$wpdb->posts AS ps
WHERE
ps.ID=cm.comment_post_ID
AND
post_status IN (‘publish’,’static’) “;

every thing is ok. but when i want to get the “user_login” from the wp_users table using this code:

$request = “SELECT ID, comment_ID, comment_content, comment_author, comment_author_url, post_title, user_login
FROM
$wpdb->comments AS cm,
$wpdb->posts AS ps,
$wpdb->users AS us
WHERE
ps.ID=cm.comment_post_ID
AND
us.ID=cm.user_id
AND
post_status IN (‘publish’,’static’) “;

the sql find no results. what am i doing wrong?