Select statement with or operator
$query = mysql_query ("SELECT * FROM `settings` WHERE user='$username' AND pass='$password'")

SELECT * FROM `settings` WHERE user='$username' AND pass='$password' or sos=$username and sos=$password

user='$username'
pass='$password'
or
sos = both $username and $password

SELECT *
FROM `settings`
WHERE (user='$username' AND pass='$password')
    or (sos='$username' and sos='$password')

SELECT *
FROM `settings`
WHERE (user='$username' AND pass='$password') or (sos='$username' and sos='$password')

SELECT *
FROM `settings`
WHERE
  (user='$username' AND pass='$password')
  OR (sos='$username' AND sos='$password')

SELECT *
FROM `settings`
WHERE
   (user='$username' AND pass='$password')
   OR
   (sos='$username' AND sos='$password')

SELECT * FROM `settings` WHERE (user='$username' AND pass='$password') or (sos=$username and sos=$password)

WHERE (user = '$username' AND pass = '$password')
OR ('$username' = '$password' AND sos = '$username');