Try:
mysql -u username -p database_name < file.sql
Check the MySQL Options.
Note-1: It is better to use a full path of a SQL file file.sql.
Note-2: Use the -R and the --triggers to keep routines and triggers of this original database. They are not copied with default.
Note-3 You may have to create an (empty) database from a MySQL if it doesn't exist already and an exported SQL doesn't contain the CREATE DATABASE (exported with --no-create-db or -n option) before you can import it.
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