You can execute the RENAME USER statement to modify the name of an account.

Syntax

RENAME USER old_user TO new_user
    [, old_user TO new_user] ...        

Example

RENAME USER account2 TO account_2;
SELECT User, Host, Password FROM mysql.user;
+----------+-----+----------------------- -+
| User     | Host| Password                |  
+----------+-----+-------------------------+
| account2 | %   | *61f3777f02386598cda****|
| account_2| %   | *0fe79c07e168cabc99b****|