How to obtain the login name of the current user using the USER() function?

USER() is a MySQL built-in function that returns the login name of the current user. Login name is defined as the combination of user name and the client IP address where you logged in from. For example:

SELECT USER();
  -- +------------------+
  -- | USER()           |
  -- +------------------+
  -- | fyi@192.168.1.11 |
  -- +------------------+

Note that the related CURRENT_USER() function returns the authentication name of user, which is a combination of "User" and "Host" columns in the mysql.user table and used to authenticate you into the system. So the authentication name returned from CURRENT_USER() may differ from the login name returned by USER(). For example:

SELECT USER(), CURRENT_USER();
  -- +------------------+----------------+
  -- | USER()           | CURRENT_USER() |
  -- +------------------+----------------+
  -- | fyi@192.168.1.11 | fyi@%          |
  -- +------------------+----------------+

SELECT User, Host, authentication_string FROM mysql.user WHERE User = 'fyi';
  -- +------+-----------+-------------------------------------------+
  -- | User | Host      | authentication_string                     |
  -- +------+-----------+-------------------------------------------+
  -- | fyi  | %         | *94BDCEBE19083CE2A1F959FD02F964C7AF4CFC29 |
  -- | fyi  | localhost | *3735F1D8464342BA852E10101E55E422EBAAAF35 |
  -- +------+-----------+-------------------------------------------+

Reference information of the USER() function:

USER(): user
  Returns the login name of the current user.

Arguments, return value and availability:
  user: Return value. The login name of the current user.
  Available since MySQL 4.0.

Related MySQL functions:

• USER() - Login Name of Current User
• SESSION_USER() - Synonym for USER()
• SYSTEM_USER() - Synonym for USER()
• CURRENT_USER() - Authentication Name of Current User

⇒ VERSION() - Version Number of MySQL Server

⇐ SYSTEM_USER() - Synonym for USER()

⇑ MySQL Functions on System Information

⇑⇑ MySQL Function References