Use this snippet to restore a SQL file in your MariaDB container:
docker-compose exec -T [container name] mysql -uroot < mydump.sql
This assumes you have not set a root password. In order to use a root password, use
docker-compose exec -T mariadb mysql -uroot -pmysecretrootpassword < mydump.sql
-T means don’t use a TTY, in other words, don’t expect interactive input. This avoids the
the input device is not a TTY
error message.