I m trying to get the database backup with condition [between two days], can anybody tell me how i make it?

Backups are basically dumb copies of data. The intelligence is actually placed in your recovery strategy. If you read up about point in time recovery this might help you. But identifying data present in the database between two dates is not a backup, this should be treated as functionality designed into your application i.e. add an additional column createddate and/or lastupdateddate and populate these fields so that using this you correctly identify the rows that have changed between two dates.

yes sir i was thinking the same, we need to add a coloumn for date and then fire queries to get the data between two dates,
one thing is more suppose that i run a query which give the data from mulitple tables, is this possile to make backup of data which i get from query, is it possible to make a backup of data which we get from any query?

No not from any query but directly from the tables themselves. I suggest you read up about the mysqldump application and look at the various options available.

thank you so much, i understand what u want to say, sir i asked a quesion regarding log file,please give some guildeline regarding that, i changed my my.cnf file but when i open mysql.log it alwasy empty, why, how i can see log file data?