The OLD_PASSWORD() function returns the value of the old (pre-MySQL 4.1) implementation of PASSWORD() as a string.
The feature allows to reset passwords for all pre-MySQL 4.1 clients that need to connect to a newer MySQL server, or any version of MariaDB, without locking them.
The OLD_PASSWORD() function returns a hashed password string computed from "String".
The return value is a string in the connection's character set.
Numeric values are interpreted as a character string.
If "String" contains no characters, the function returns an empty string.
If the value of "String" is NULL, the OLD_PASSWORD() function returns NULL.
MySQL does not support this MariaDB feature.