MYSQL 4.1以後, 采用了一種新的用戶認證協議, 對於老的客戶端會出現不支持認證協議的錯誤, 以下是官方網站的解決方法﹔
１Upgrade all client programs to use a 4.1.1 or newer client library.
更新客戶端庫，這需要更新PHP的擴展庫，對於老的api PHP已經不提供了這樣的擴展庫了
２When connecting to the server with a pre-4.1 client program, use an account that still has a pre-4.1-style password.
使用以前建立的賬號連接，對於在新的認證協議下建立的賬戶就不行了
３Reset the password to pre-4.1 style for each user that needs to use a pre-4.1 client program. This can be done using the SET PASSWORD statement and the OLD_PASSWORD() function: mysql> SET PASSWORD FOR
-> 'some_user'@'some_host' = OLD_PASSWORD('newpwd');
Alternatively, use UPDATE and FLUSH PRIVILEGES: mysql> UPDATE mysql.user SET Password = OLD_PASSWORD('newpwd') -> WHERE Host = 'some_host' AND User = 'some_user';
mysql> FLUSH PRIVILEGES;
Substitute the password you want to use for ``newpwd'' in the preceding examples. MySQL cannot tell you what the original password was, so you'll need to pick a new one.
這是一個不錯的辦法，新建立的賬號采用老式的加密協議
４Tell the server to use the older password hashing algorithm:
Start mysqld with the --old-passwords option.
這樣新認證協議的優點就沒法使用了
５Assign an old-format password to each account that has had its password updated to the longer 4.1 format. You can identify these accounts with the following query: mysql> SELECT Host, User, Password FROM mysql.user
-> WHERE LENGTH(Password) > 16;
For each account record displayed by the query, use the Host and User values and assign a password using the OLD_PASSWORD() function and either SET PASSWORD or UPDATE, as described earlier.
恢復已經升級了口令到老樣式
