MySQL on duplicate key update

Question

If I have query like this, how can I refer to values I have already given in update statement, so that I don\'t need to insert same data to query again? Example I would like

Answer 1

In PHP I do this to solve the issue:

$fields = "a = 1, b = 2, c = 3";
$sql = "INSERT INTO some_table SET id = $id, $fields ON DUPLICATE KEY UPDATE $fields";
mysql_query($sql);