How to verify if given user@host with 'password' exists in MySQL 8.0+?
Actually, there is an alternative that MySQL (really Oracle) does not mention.


Back on Apr 22, 2015, I posted the Algorithm for the Password Function
MySQL 8.0 will still store the PASSWORD function output in the authentication_string column if you create the user using the mysql_native_password plugin.


Here is the algorithm

SET @plaintextpassword = 'whatever password you want';
SELECT CONCAT('*',UPPER(SHA1(UNHEX(SHA1(@plaintextpassword)))));


GIVING CREDIT

I first learned this from a blog by a company called PalominoDB. They changed their name to blackbird. Pythian purchased blackbird. Pythian now has it as a blog post with this algorithm : Hashing Algorithm in MySQL PASSWORD()