Alter existing user options.
Superusers can change a user's password or superuser status. To prevent disabling all superusers, superusers cannot change their own superuser status. Ordinary users can change only their own password.
Enclose the user name in single quotation marks if it contains non-alphanumeric characters. Enclose the password in single quotation marks.
Example
ALTER USER moss WITH PASSWORD 'bestReceiver';