automatic_config_schema_conf_config.yaml

defaults:
  - db: mysql

automatic_config_schema_conf_db_mysql.yaml

# @package _group_
defaults:
  - schema/db/mysql
  - _self_

host: localhost
port: 3306
driver: mysql
user: omry
password: secret

automatic_config_schema_conf_db_postgresql.yaml

# @package _group_
defaults:
  - schema/db/postgresql
  - _self_

host: localhost
port: 5432
driver: postgresql
user: postgre_user
password: secret
timeout: 10

automatic_config_schema_my_app.py

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
from dataclasses import dataclass

from omegaconf import OmegaConf, DictConfig

import hydra
from hydra.core.config_store import ConfigStore


@dataclass
class MySQLConfig:
    host: str
    port: int
    user: str
    password: str
    driver: str = "mysql"


@dataclass
class PostGreSQLConfig:
    host: str
    port: int
    timeout: int
    user: str
    password: str
    driver: str = "postgresql"


cs = ConfigStore.instance()
cs.store(group="schema/db", name="mysql", node=MySQLConfig, package="db")
cs.store(group="schema/db", name="postgresql", node=PostGreSQLConfig, package="db")


@hydra.main(config_path="conf", config_name="config")
def my_app(cfg: DictConfig) -> None:
    print(OmegaConf.to_yaml(cfg))


if __name__ == "__main__":
    my_app()

Structure:

examples/advanced/automatic_config_schema
├── conf
│   ├── config.yaml
│   └── db
│       ├── mysql.yaml
│       └── postgresql.yaml
└── my_app.py

Example outputs:

omry@Coronadev:~/dev/hydra$ python examples/advanced/automatic_config_schema/my_app.py  
db:
  host: localhost
  port: 3306
  user: omry
  password: secret
  driver: mysql

omry@Coronadev:~/dev/hydra$ python examples/advanced/automatic_config_schema/my_app.py  db.port=aaa
Error merging override db.port=aaa
Value 'aaa' could not be converted to Integer
        full_key: db.port
        reference_type=Optional[MySQLConfig]
        object_type=MySQLConfig

Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.
omry@Coronadev:~/dev/hydra$ python examples/advanced/automatic_config_schema/my_app.py db=postgresql db.port=aaa
Error merging override db.port=aaa
Value 'aaa' could not be converted to Integer
        full_key: db.port
        reference_type=Optional[PostGreSQLConfig]
        object_type=PostGreSQLConfig

Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.