Keep in mind this no longer works if you’re running Plesk 11 and have enabled the enhanced security mode which encrypts the passwords stored in the database.

SELECT
   data_bases.name,
   db_users.login,
   accounts.password
FROM data_bases, db_users, accounts
WHERE
   data_bases.default_user_id = db_users.id AND
   db_users.account_id = accounts.id;