Syntax:
ALTER USER user_specification [, user_specification] ...

user_specification:
    user PASSWORD EXPIRE

The ALTER USER statement modifies MySQL accounts. An error occurs if
you try to modify a nonexistent account.

To use ALTER 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, ALTER USER additionally requires the SUPER
privilege.

*Warning*: ALTER USER was added in MySQL 5.6.6. However, in 5.6.6,
ALTER USER also sets the Password column to the empty string, so do not
use this statement until 5.6.7.

Each account name uses the format described in
http://dev.mysql.com/doc/refman/5.6/en/account-names.html. If you
specify only the user name part of the account name, a host name part
of '%' is used. It is also possible to specify CURRENT_USER or
CURRENT_USER() to refer to the account associated with the current
session.

For each account, ALTER USER expires its password. For example:

ALTER USER 'jeffrey'@'localhost' PASSWORD EXPIRE;

Password expiration for an account affects the corresponding row of the
mysql.user table: The server sets the password_expired column to 'Y'.

A client session operates in restricted mode if the account password
has been expired. In restricted mode, operations performed within the
session result in an error until the user establishes a new account
password:

mysql> SELECT 1;
ERROR 1820 (HY000): You must SET PASSWORD before executing this statement

mysql> SET PASSWORD = PASSWORD('new_password');
Query OK, 0 rows affected (0.01 sec)

mysql> SELECT 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

As of MySQL 5.6.8, this restricted mode of operation permits SET
statements, which is useful if the account password has a hashing
format that requires old_passwords to be set to a value different from
its default before using SET PASSWORD.

It is possible for an administrative user to reset the account
password, but any existing sessions for the account remain restricted.
A client using the account must disconnect and reconnect before
statements can be executed successfully.

*Note*: It is possible to "reset" a password by setting it to its
current value. As a matter of good policy, it is preferable to choose a
different password.

URL: http://dev.mysql.com/doc/refman/5.6/en/alter-user.html

