Start with standard docker-compose file.

version: "3.7"
services:
    mariadb:
        build:
            context: .
            dockerfile: dev.dockerfile
        restart: always
        environment:
            MYSQL_ROOT_PASSWORD: password
            MYSQL_DATABASE: db_name
            MYSQL_USER: sql_user
            MYSQL_PASSWORD: password
        ports:
            - 3306:3306

Add dev.dockerfile:

FROM mariadb:latest

ADD init.sql /docker-entrypoint-initdb.d/ddl.sql

Finally, add your init.sql file. Let’s give all privileges to our sql_user:

GRANT ALL PRIVILEGES ON *.* TO 'sql_user'@'%';

Now, run docker-compose build, then docker-compose up.

Access from another container

If you want to access the database container from other containers, while running them separately, you can specify host.docker.internal as the address of your database.

If you’re on linux, then you need docker engine >= 20.03, and you need to add to your docker-compose file:

  my_app:
    extra_hosts:
      - "host.docker.internal:host-gateway"

If you’re are on Mac ^^ will break your setup unless you are at least on Docker Desktop for Mac 3.3.0. See Support host.docker.internal DNS name to host · Issue #264 · docker/for-linux (github.com) for details.