Syntax:
OLD_PASSWORD(str)

OLD_PASSWORD() was added when the implementation of PASSWORD() was
changed in MySQL 4.1 to improve security. OLD_PASSWORD() returned the
value of the pre-4.1 implementation of PASSWORD() as a string, and was
intended to permit you to reset passwords for any pre-4.1 clients that
need to connect to your MySQL server without locking them out. See
https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html.

Passwords that use the pre-4.1 hashing method are less secure than
passwords that use the native password hashing method. Support for
pre-4.1 passwords was removed in MySQL 5.7.5, as was OLD_PASSWORD().

URL: https://dev.mysql.com/doc/refman/5.7/en/encryption-functions.html

