To assign or change a password for an existing account, one way is to issue a SET PASSWORD statement:

mysql> SET PASSWORD FOR 'jeffrey'@'localhost' = PASSWORD('biscuit');

Only users such as root that have update access to the mysql database can change the password for other users. If you are not connected as an anonymous user, you can change your own password by omitting the FOR clause:

mysql> SET PASSWORD = PASSWORD('biscuit');

You can also use a GRANT USAGE statement at the global level (ON *.*) to assign a password to an account without affecting the account's current privileges:

mysql> GRANT USAGE ON *.* TO 'jeffrey'@'localhost' IDENTIFIED BY 'biscuit';

Passwords can be assigned from the command line by using the mysqladmin command:

shell> mysqladmin -u user_name -h host_name password "newpwd"

The account for which this command resets the password is the one with a user table row that matches user_name in the User column and the client host from which you connect in the Host column.

Although it is generally preferable to assign passwords using one of the preceding methods, you can also do so by modifying the user table directly:

When you assign passwords using GRANT with an IDENTIFIED BY clause or with the mysqladmin password command, they take care of encrypting the password for you.

When you assign an account a nonempty password using SET PASSWORD, INSERT, or UPDATE, you must use the PASSWORD() function to encrypt the password. PASSWORD() is necessary because the user table stores passwords in encrypted form, not as plaintext. If you forget that fact, you are likely to set passwords like this:

shell> mysql -u root mysql
mysql> INSERT INTO user (Host,User,Password)
    -> VALUES('localhost','jeffrey','biscuit');
mysql> FLUSH PRIVILEGES;

The result is that the literal value 'biscuit' is stored as the password in the user table, not the encrypted value. When jeffrey attempts to connect to the server using this password, the value is encrypted and compared to the value stored in the user table. However, the stored value is the literal string 'biscuit', so the comparison fails and the server rejects the connection:

shell> mysql -u jeffrey -pbiscuit test
Access denied