I did a big mistake that I updated a table without \'where\' clause in MySQL :\'(
It is auto-committed.
Is there any way to rollback from it?
Look up transaction logs. I'll update with more info but the logs may only stay around for a limited time so time is of the essence!
See: http://dev.mysql.com/doc/refman/5.0/en/point-in-time-recovery.html
If you have enabled mysql binlog and also it is of ROW based format, then you can get the value for each row before & after the update. Using that you can restore the table's state.
No, there's no query that will "undo" a committed data-modifying query.
If you have a backup of the database, you can restore the backup and use DBA tools (in MySQL's case, it's mysqlbinlog) to "replay" all data-modifying queries from the logs since the backup back to the database, but skip over the problem query.
If you don't have a backup and all logs since the that backup, there's nothing you can do to recover the data.