SET PASSWORD [FOR user] =
    {
        PASSWORD('some password')
      | OLD_PASSWORD('some password')
      | 'encrypted password'
    }

The SET PASSWORD statement assigns a password to an existing MySQL user account.

If the password is specified using the PASSWORD() or OLD_PASSWORD() function, the literal text of the password should be given. If the password is specified without using either function, the password should be the already-encrypted password value as returned by PASSWORD().

With no FOR clause, this statement sets the password for the current user. Any client that has connected to the server using a nonanonymous account can change the password for that account.

With a FOR clause, this statement sets the password for a specific account on the current server host. Only clients that have the UPDATE privilege for the mysql database can do this. The user value should be given in user_name@host_name format, where user_name and host_name are exactly as they are listed in the User and Host columns of the mysql.user table entry. For example, if you had an entry with User and Host column values of 'bob' and '%.loc.gov', you would write the statement like this:

SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

That is equivalent to the following statements:

UPDATE mysql.user SET Password=PASSWORD('newpass')
  WHERE User='bob' AND Host='%.loc.gov';
FLUSH PRIVILEGES;

Starting from MySQL 4.1, you can see which account the server authenticated you as by executing SELECT CURRENT_USER().