TABLE users
userid   firstname    lastname
1         JOHN         DEO
2         JANE         DEO

TABLE msg
msg_id    msg_from     msg_to      received   age  city  country

##</code><code>##

SELECT users.userid, users.firstname, users.lastname, msg.age, msg.city, msg.country FROM msg
JOIN users ON users.userid = msg.msg_from
WHERE msg.msg_to = ? 
  AND msg.received IS NULL