I have a docker mysql image running, following is what the docker-compose.yml file looks like:
db:
image: mysql
environment:
MYSQL_ROOT_PASSWORD: \"\
Connect to MySQL via {host ip}:3306 since you've exposed the internal port to your host as 3306. If you need to access the MySQL CLI tools you will need to go docker exec -it mycontainer bash this will place you inside the container to access the tools installed with MySQL if you do not have them installed locally on the host o/s.