mysql query

i need a simple mysql query. there are two tables. one is user (id, name) the other one is blocked (blocker, blocked) i need a query that selects users from the user table that are NOT blocked by a certain user (whose id is stored in a session variable) i tried $query="SELECT user.user_username, user.user_id FROM blocked LEFT JOIN (user ON [login to view URL] user.user_id AND [login to view URL] '".$_SESSION['useris']."'" but it didn't work. obviously:)