I am using phpmyadmin on my windows os. I have a database with one table which has 100M records with the size of 20GB. I want to export this table and have the table.sql fil
If you are on a shared hosting or you don't have access to shell, then use mysqldumper script; copy it to your server and start it in your browser under "yourDomain.com/path_to_mysqlumper/"
MySQLDumper is a PHP and Perl based tool for backing up MySQL databases. You can easily dump your data into a backup file and - if needed - restore it. It is especially suited for shared hosting webspaces, where you don't have shell access.
If you have shell access to your host servers (if provided by your host since not all shared server hosters give this access) then you may use SSH access like in this tutorial using Putty that you install and configure then import or export your databases like in this third tutorial.