Docker-compose MySQL Image create multiple databases

docker-compose.yml

  # The official MySQL (https://hub.docker.com/_/mysql/) supports only one MYSQL_DATABASE environment variable.
  # By modifying the entrypoint and passing shell script, you can create multiple dbs without having to make a mysql image just for this purpose.
  
version: '3'

services:
  # Some other service connecting to mysql
  
  db:
    image: mysql:5.6
    environment:
      - MYSQL_USER=root
      - MYSQL_ALLOW_EMPTY_PASSWORD=yes
    entrypoint:
      sh -c "
        echo 'CREATE DATABASE IF NOT EXISTS firstDB; CREATE DATABASE IF NOT EXISTS secondDB;' > /docker-entrypoint-initdb.d/init.sql;
        /usr/local/bin/docker-entrypoint.sh --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
      "
    ports:
      - 3306:3306 

there is very well explained tutorial for the multiple databases found which works perfect
https://medium.com/@onexlab.io/docker-compose-mysql-multiple-database-fe640938e06b