Syntax:
SYSTEM_USER()

SYSTEM_USER() is a synonym for USER().

*Note*:

The SYSTEM_USER() function is distinct from the SYSTEM_USER privilege.
The former returns the current MySQL account name. The latter
distinguishes the system user and regular user account categories (see
https://dev.mysql.com/doc/refman/8.4/en/account-categories.html).

URL: https://dev.mysql.com/doc/refman/8.4/en/information-functions.html

