user deletion

$query->( "
DELETE
    U, SB, S, O
FROM
    users AS U
INNER JOIN
    shopping_bag AS SB
INNER JOIN
    settings AS S
INNER JOIN
    orders AS O
WHERE
    U.id           = " . MySQLiDatabase::getInstance()->escapeValue( getPost( 'selected_user' ) ) . " AND
    SB.customer_id = U.id AND
    S.customer_id  = U.id AND
    O.customer_id  = U.id
" );