[, old_user TO new_user] …
The RENAME USER statement renames existing MySQL accounts. An error occurs for old accounts that do not exist or new accounts that already exist.
To use RENAME USER, you must have the global CREATE USER privilege, or the UPDATE privilege for the mysql database. When the read_only system variable is enabled, RENAME USER additionally requires the SUPER privilege.
Each account name uses the format described in Section 7.2.3, “Specifying Account Names”. For example:
RENAME USER ‘jeffrey’@’localhost’ TO ‘jeff’@’127.0.0.1’;
The host name part of the account name, if omitted, defaults to ‘%’.
RENAME USER causes the privileges held by the old user to be those held by the new user. However, RENAME USER does not automatically drop or invalidate databases or objects within them that the old user created. This includes stored programs or views for which the DEFINER attribute names the old user. Attempts to access such objects may produce an error if they execute in definer security context. (For information about security context, see Section 22.6, “Access Control for Stored Programs and Views”.)
The privilege changes take effect as indicated in Section 7.2.6, “When Privilege Changes Take Effect”.