PASSWORD(str)
Calculates and returns a password string from the plaintext password str, or NULL if the argument was NULL. This is the function that is used for encrypting MySQL passwords for storage in the Password column of the user grant table.

mysql> SELECT PASSWORD('badpwd');
-> '7f84554057dd964b'

PASSWORD() encryption is one-way (not reversible). PASSWORD() does not perform password encryption in the same way that Unix passwords are encrypted. See ENCRYPT(). Note: The PASSWORD() function is used by the authentication system in MySQL Server, you should not use it in your own applications. For that purpose, use MD5() or SHA1() instead. Also see RFC 2195 for more information about handling passwords and authentication securely in your application.
Significa che una volta che l'hai crittata non puoi più recuperarla. L'unico modo che hai è creare una nuova password ed inviarla all'utente provvedendo ad aggiornare il campo.
La prossima volta google oppure il sito di riferimento!