Table ‘tmedia.a54fT_6_users’ doesn’t exist

I am getting the database error Table ‘tmedia.a54fT_6_users’ doesn’t exist.
The query is:
SELECT DISTINCT u.ID, u.display_name
FROM a54fT_6_posts p
INNER JOIN a54fT_6_users u
ON p.post_author = u.ID
AND post_status NOT IN (‘trash’)
WHERE post_type = ‘attachment’
ORDER BY u.display_name ASC

Any suggestions how to fix?