Two different doke-compose instances?

Question

Docker

There are two directories, one for running the database, the other for running the web application, how to link the application with the database? For example, through depends_on ..
I don’t want to touch External_links, it is tied to the container, as far as I know
. I tried to do it through networks, but I didn’t understand how to handle it ..
DB:

version: '2'
services:
    mysql:
        image: mysql:5.7
        environment:
            - MYSQL_ROOT_PASSWORD=root
        volumes:
            - ./data/mysql_db:/var/lib/mysql
        ports:
            - "33060:3306"

Appendix:

version: '2'
services:
    redmine:
        image: redmine:3.3.2
        ports:
          - 8080:3000
        environment:
          REDMINE_DB_MYSQL: mysql
          REDMINE_DB_PASSWORD: root
        volumes:
            - ./data/redmine:/usr/src/redmine/files

Answer 1

version: '2'

services:

  redmine:
    image: redmine
    ports:
      - 8080:3000
    environment:
      REDMINE_DB_MYSQL: db
      REDMINE_DB_PASSWORD: example
    depends_on:
      - db
    restart: always

  db:
    image: mariadb
    environment:
      MYSQL_ROOT_PASSWORD: example
      MYSQL_DATABASE: redmine
    restart: always