Differences between mysql user functions

I can only talk about my food. I found it on the Internet and didn't find anyone explaining the four differences between them, so I had to do it myself. The following is the help information you can view on the mysql client.

User: Returns the current MySQL username and hostname as a string in the utf8 character set.

System_user: SYSTEM_USER () is a synonym for USER ().

Session_user: SESSION_USER () is a synonym for USER ().

Current_user:

Returns the username and hostname combination for the MySQL account

That the server used to authenticate the current client. This account

Determines your access privileges. As of MySQL 5.0.10, within a stored

Routine that is defined with the SQL SECURITY DEFINER characteristic,

CURRENT_USER () returns the creator of the routine. The return value is

A string in the utf8 character set.

The value of CURRENT_USER () can differ from the value of USER ().

In fact, if I want to try again, I will not translate it if I can't see anyone's English skills. In general, user (), system_user (), and session_user () are the same thing (synonym ). Then current_user () is similar to the first three, but occasionally it will be a little different.