mysql -u username -p database_name < file.sql
Note:It is better to use the full path of the SQL file file.sql. Use -R and --triggers to keep the routines and triggers of original database. They are not copied by default.
You may have to create the (empty) database from mysql if it doesn't exist already and the exported SQL don't contain CREATE DATABASE (exported with --no-create-db or -n option), before you can import it.
Hope it helps!!