Was your backup in the form of SQL statements to execute? Or did you just replace the data files with the older versions?
If it was done by SQL statements, then you may still have a transaction log around that you can use. I don't know the details, or even if you'll be able to fix it, but you could google for something like mysql transaction log or mysql recovery or something like that.
Actually my back is a .sql file which was taken by mysqldump command(mysqldump -u username -pPASSWORD pPASSWORD >/mnt/abc_23oct2012.sql)
This was done 1 week ago.Today i accidently run the command mysql -u username -pPASSWORD pPASSWORD < /mnt/abc_23oct2012.sql
So what happend is that i lost i week data from my db.So what should i do to recover the lost data? please help me...
OP, try what other(s) already suggested. But I wouldn't be optimistic about retreiving old data since you didn't create a backup before you updated database. Since autocommit is enabled by default (source) all (create, update, delete) statements are commited as soon as they completed successfully, so I suppose there is no way to do a rollback.
The quieter you are, the more you are able to hear.