Specifying a db function in an insert statement in Zend

I have something like this:

$data = array('use开发者_开发技巧rname' => 'John', 'password' => 'john123');
$table = new Zend_Db_Table('users');
$table->insert($data);

But I want it to include a hashing function to the password, so the sql is something like this:

INSERT INTO `users` (`username`, `password`) VALUES ('John', PASSWORD('john123'));

How can I do that, elegantly?

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$data = array('username' => 'John', 'password' => new Zend_Db_Expr('SHA1(john123)');