Try like this:
I think you need to use the full path at the command line, something like this, perhaps:
C:\xampp\mysql\bin\mysql -u {username} -p {databasename} < file_name.sql
Refer this link also:
http://www.ryantetek.com/2011/09/importing-large-sql-files-through-command-line-when-using-phpmyadminxampp/