docs(readme): DB connection examples for PostgreSQL, MySQL, MSSQL (all ORMs)

README.md

@@ -46,6 +46,215 @@ pip install "fastapi-viewsets[test]"   # pytest, httpx, coverage, etc.
 
 For async SQLAlchemy you still need a driver such as `aiosqlite`, `asyncpg`, or `aiomysql` alongside your database URL.
 
+## Database connection examples
+
+`fastapi-viewsets` doesn't bundle DB drivers — you pick them per stack.
+The table below maps each ORM to the install command, the driver(s)
+you need, and the URL shape for **PostgreSQL**, **MySQL**, and
+**Microsoft SQL Server**.
+
+| ORM | PostgreSQL | MySQL | MSSQL |
+| --- | --- | --- | --- |
+| **SQLAlchemy (sync)** | `psycopg[binary]` or `psycopg2-binary` | `pymysql` or `mysqlclient` | `pyodbc` + ODBC Driver 17/18 |
+| **SQLAlchemy (async)** | `asyncpg` | `aiomysql` or `asyncmy` | `aioodbc` + ODBC Driver 17/18 |
+| **Tortoise ORM** | `asyncpg` (built-in) | `aiomysql` (built-in) | Not supported by Tortoise |
+| **Peewee** | `psycopg2-binary` | `pymysql` or `mysqlclient` | Not supported by this adapter |
+
+> The `SQLAlchemyAdapter` auto-converts a sync URL to its async
+> counterpart (`postgresql://` → `postgresql+asyncpg://`,
+> `mysql://` → `mysql+aiomysql://`, `sqlite:///` →
+> `sqlite+aiosqlite:///`). For MSSQL you have to set the async URL
+> explicitly via `SQLALCHEMY_ASYNC_DATABASE_URL`. If the matching async
+> driver is not installed, `SQLAlchemyAdapter` falls back to sync-only
+> mode and `get_async_session()` raises a helpful `RuntimeError`
+> (since v1.2.1).
+
+The library reads database configuration from environment variables
+(loaded via `python-dotenv` from `.env`). Pick the ORM with `ORM_TYPE`,
+then set the URL with `<ORM>_DATABASE_URL` (or the generic
+`DATABASE_URL`).
+
+### SQLAlchemy (sync and async)
+
+```bash
+# PostgreSQL
+pip install "fastapi-viewsets[sqlalchemy]" "psycopg[binary]" asyncpg
+
+# MySQL
+pip install "fastapi-viewsets[sqlalchemy]" pymysql aiomysql
+
+# MSSQL (needs Microsoft ODBC Driver 17 or 18 on the host)
+pip install "fastapi-viewsets[sqlalchemy]" pyodbc aioodbc
+```
+
+Example `.env` (one block at a time):
+
+```dotenv
+# --- PostgreSQL ---
+ORM_TYPE=sqlalchemy
+SQLALCHEMY_DATABASE_URL=postgresql+psycopg://user:pass@db.example.com:5432/app
+# Optional explicit async URL; otherwise auto-derived to postgresql+asyncpg://
+SQLALCHEMY_ASYNC_DATABASE_URL=postgresql+asyncpg://user:pass@db.example.com:5432/app
+
+# --- MySQL ---
+ORM_TYPE=sqlalchemy
+SQLALCHEMY_DATABASE_URL=mysql+pymysql://user:pass@db.example.com:3306/app?charset=utf8mb4
+SQLALCHEMY_ASYNC_DATABASE_URL=mysql+aiomysql://user:pass@db.example.com:3306/app?charset=utf8mb4
+
+# --- MSSQL ---
+ORM_TYPE=sqlalchemy
+# URL-encode the ODBC driver name ("+" instead of spaces).
+SQLALCHEMY_DATABASE_URL=mssql+pyodbc://user:pass@db.example.com:1433/app?driver=ODBC+Driver+18+for+SQL+Server&Encrypt=yes&TrustServerCertificate=no
+SQLALCHEMY_ASYNC_DATABASE_URL=mssql+aioodbc://user:pass@db.example.com:1433/app?driver=ODBC+Driver+18+for+SQL+Server&Encrypt=yes&TrustServerCertificate=no
+```
+
+Use `BaseViewset` for sync code or `AsyncBaseViewset` for async code
+(see the [Async quickstart](#async-quickstart-sqlalchemy-2x--pydantic-v2)
+below).
+
+### Tortoise ORM
+
+Tortoise is async-only. The adapter takes a database URL plus a list
+of model modules to register on startup.
+
+```bash
+# PostgreSQL
+pip install "fastapi-viewsets[tortoise]"          # pulls in asyncpg
+
+# MySQL
+pip install "fastapi-viewsets[tortoise]" aiomysql
+```
+
+```dotenv
+# --- PostgreSQL ---
+ORM_TYPE=tortoise
+TORTOISE_DATABASE_URL=postgres://user:pass@db.example.com:5432/app
+TORTOISE_MODELS=["app.models"]
+TORTOISE_APP_LABEL=models
+
+# --- MySQL ---
+ORM_TYPE=tortoise
+TORTOISE_DATABASE_URL=mysql://user:pass@db.example.com:3306/app
+TORTOISE_MODELS=["app.models"]
+TORTOISE_APP_LABEL=models
+```
+
+```python
+from fastapi import FastAPI
+from tortoise import Tortoise
+
+from fastapi_viewsets import AsyncBaseViewset
+from fastapi_viewsets.orm.factory import ORMFactory
+
+app = FastAPI()
+adapter = ORMFactory.get_default_adapter()  # built from the env vars above
+
+
+@app.on_event("startup")
+async def _init_tortoise() -> None:
+    """Open the Tortoise connection pool and create schema if needed.
+
+    The adapter also initializes Tortoise lazily on first DB call;
+    doing it here gives you control over schema creation.
+    """
+    await Tortoise.init(
+        db_url=adapter.database_url,
+        modules={adapter.app_label: adapter.models},
+    )
+    await Tortoise.generate_schemas(safe=True)
+
+
+@app.on_event("shutdown")
+async def _close_tortoise() -> None:
+    """Close the Tortoise connection pool."""
+    await Tortoise.close_connections()
+
+
+# Define your Tortoise models in app/models.py and pass them to AsyncBaseViewset.
+# from app.models import Item
+# from app.schemas import ItemSchema
+# items = AsyncBaseViewset(
+#     endpoint="/items",
+#     model=Item,
+#     response_model=ItemSchema,
+#     db_session=adapter.get_async_session,
+#     orm_adapter=adapter,
+#     tags=["items"],
+# )
+# items.register(methods=["LIST", "GET", "POST", "PATCH", "DELETE"])
+# app.include_router(items)
+```
+
+> **MSSQL is not supported by Tortoise ORM.** Use SQLAlchemy with
+> `aioodbc` for SQL Server.
+
+### Peewee
+
+Peewee is sync-only. The adapter parses the URL and instantiates the
+right `Database` class.
+
+```bash
+# PostgreSQL
+pip install "fastapi-viewsets[peewee]" psycopg2-binary
+
+# MySQL
+pip install "fastapi-viewsets[peewee]" pymysql
+```
+
+```dotenv
+# --- PostgreSQL ---
+ORM_TYPE=peewee
+PEEWEE_DATABASE_URL=postgresql://user:pass@db.example.com:5432/app
+
+# --- MySQL ---
+ORM_TYPE=peewee
+PEEWEE_DATABASE_URL=mysql://user:pass@db.example.com:3306/app
+```
+
+```python
+from fastapi import FastAPI
+
+from fastapi_viewsets import BaseViewset
+from fastapi_viewsets.orm.factory import ORMFactory
+
+app = FastAPI()
+adapter = ORMFactory.get_default_adapter()  # built from the env vars above
+
+# from app.models import Item            # peewee.Model subclass
+# from app.schemas import ItemSchema     # Pydantic v2 schema
+# items = BaseViewset(
+#     endpoint="/items",
+#     model=Item,
+#     response_model=ItemSchema,
+#     db_session=adapter.get_session,
+#     orm_adapter=adapter,
+#     tags=["items"],
+# )
+# items.register(methods=["LIST", "GET", "POST", "PATCH", "DELETE"])
+# app.include_router(items)
+```
+
+> **MSSQL is not supported by this Peewee adapter** (the URL parser
+> only handles `sqlite:///`, `postgresql://`, `postgres://`,
+> `mysql://`). For SQL Server, use SQLAlchemy.
+
+### Building the adapter from code (no env vars)
+
+When you don't want to rely on environment variables, instantiate the
+adapter directly and pass it to the viewset via `orm_adapter=`:
+
+```python
+from fastapi_viewsets.orm.factory import ORMFactory
+
+adapter = ORMFactory.create_adapter(
+    "sqlalchemy",
+    {
+        "database_url": "postgresql+psycopg://user:pass@db.example.com:5432/app",
+        "async_database_url": "postgresql+asyncpg://user:pass@db.example.com:5432/app",
+    },
+)
+```
+
 ## Quickstart (SQLAlchemy, sync)
 
 Save as `main.py` in an empty folder and run `python main.py` or `uvicorn main:app --reload`.