Postgres Docker Multiple Database

docker-compose.yml

version: '3.6'
services: 
    postgres:
        image: postgres
        restart: always
        environment: 
            - DATABASE_HOST=127.0.0.1
            - POSTGRES_USER=root
            - POSTGRES_PASSWORD=root
            - POSTGRES_DB=root  

        ports: 
            - "5432:5432"
        volumes: 
            - ./docker_postgres_init.sql:/docker-entrypoint-initdb.d/docker_postgres_init.sql
    
    pgadmin-compose:
        image: dpage/pgadmin4
        environment: 
            PGADMIN_DEFAULT_EMAIL: "[email protected]"
            PGADMIN_DEFAULT_PASSWORD: "test123!"
        ports: 
            - "16543:80"
        depends_on: 
            - postgres