MySQL 4.1 and up uses an authentication protocol based on a password hashing algorithm that is incompatible with that used by older clients. .....

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如果你升级mysql到4.1以上版本后遇到以上问题,请先确定你的mysql client 是4.1或者更高版本.(WINDOWS下有问题你就直接跳到下面看解决方法了,因为MYSQL 在WINDOWS是client和server一起装上了的)

请使用以下两种方法之一

其一:

mysql> SET PASSWORD FOR
    -> 'some_user'@'some_host' = OLD_PASSWORD('newpwd');

其二:

mysql> UPDATE mysql.user SET Password = OLD_PASSWORD('newpwd')
    -> WHERE Host = 'some_host' AND User = 'some_user';
mysql> FLUSH PRIVILEGES;

上面红色的部分请按自己实际情况修改....

这样做后,连接就会正常了@!