Use native CP mysql inside a docker container

Hello everybody,
I’ve set successfully a redmine container in CP and used the reverse proxy function with success (Reverse Proxy Traffic to Docker Container on CyberPanel - CyberPanel).

Redmine use a MySql database so I thought I could use a db created on the associated reverse proxy CP domain.

Unfortunately I am unable to connect with my sql: I’ve been trying with localhost and 127.0.0.1, with db-user and also with mySql root user.
I have an access denied error.

Am I trying to do something impossible or is there some special configuration to let container speak with native CP mySql?

Thank you if you have any idea on this …
JC