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# SQLAlchemy

FastAPI Users provides the necessary tools to work with SQL databases thanks to SQLAlchemy ORM with asyncio.

Warning

The previous adapter using `encode/databases` is now deprecated but can still be installed using `fastapi-users[sqlalchemy]`.

## Asynchronous driver

To work with your DBMS, you'll need to install the corresponding asyncio driver. The common choices are:

- For PostgreSQL: `pip install asyncpg`
- For SQLite: `pip install aiosqlite`

For the sake of this tutorial from now on, we'll use a simple SQLite databse.

## Setup User table

Let's declare our SQLAlchemy `User` table.

    from typing import AsyncGenerator

    from fastapi import Depends
    from fastapi_users.db import SQLAlchemyBaseUserTable, SQLAlchemyUserDatabase
    from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
    from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base
    from sqlalchemy.orm import sessionmaker

    from .models import UserDB

    DATABASE_URL = "sqlite+aiosqlite:///./test.db"
    Base: DeclarativeMeta = declarative_base()

    class UserTable(Base, SQLAlchemyBaseUserTable):
        pass

    engine = create_async_engine(DATABASE_URL)
    async_session_maker = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

    async def create_db_and_tables():
        async with engine.begin() as conn:
            await conn.run_sync(Base.metadata.create_all)

    async def get_async_session() -> AsyncGenerator[AsyncSession, None]:
        async with async_session_maker() as session:
            yield session

    async def get_user_db(session: AsyncSession = Depends(get_async_session)):
        yield SQLAlchemyUserDatabase(UserDB, session, UserTable)

As you can see, FastAPI Users provides a mixin that will include base fields for our `User` table. You can of course add you own fields there to fit to your needs!

## Implement a function to create the tables

We'll now create an utility function to create all the defined tables.

    from typing import AsyncGenerator

    from fastapi import Depends
    from fastapi_users.db import SQLAlchemyBaseUserTable, SQLAlchemyUserDatabase
    from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
    from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base
    from sqlalchemy.orm import sessionmaker

    from .models import UserDB

    DATABASE_URL = "sqlite+aiosqlite:///./test.db"
    Base: DeclarativeMeta = declarative_base()

    class UserTable(Base, SQLAlchemyBaseUserTable):
        pass

    engine = create_async_engine(DATABASE_URL)
    async_session_maker = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

    async def create_db_and_tables():
        async with engine.begin() as conn:
            await conn.run_sync(Base.metadata.create_all)

    async def get_async_session() -> AsyncGenerator[AsyncSession, None]:
        async with async_session_maker() as session:
            yield session

    async def get_user_db(session: AsyncSession = Depends(get_async_session)):
        yield SQLAlchemyUserDatabase(UserDB, session, UserTable)

This function can be called, for example, during the initialization of your FastAPI app.

Warning

In production, it's strongly recommended to setup a migration system to update your SQL schemas. See Alembic.

## Create the database adapter dependency

The database adapter of FastAPI Users makes the link between your database configuration and the users logic. It should be generated by a FastAPI dependency.

    from typing import AsyncGenerator

    from fastapi import Depends
    from fastapi_users.db import SQLAlchemyBaseUserTable, SQLAlchemyUserDatabase
    from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
    from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base
    from sqlalchemy.orm import sessionmaker

    from .models import UserDB

    DATABASE_URL = "sqlite+aiosqlite:///./test.db"
    Base: DeclarativeMeta = declarative_base()

    class UserTable(Base, SQLAlchemyBaseUserTable):
        pass

    engine = create_async_engine(DATABASE_URL)
    async_session_maker = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

    async def create_db_and_tables():
        async with engine.begin() as conn:
            await conn.run_sync(Base.metadata.create_all)

    async def get_async_session() -> AsyncGenerator[AsyncSession, None]:
        async with async_session_maker() as session:
            yield session

    async def get_user_db(session: AsyncSession = Depends(get_async_session)):
        yield SQLAlchemyUserDatabase(UserDB, session, UserTable)

Notice that we define first a `get_async_session` dependency returning us a fresh SQLAlchemy session to interact with the database.

It's then used inside the `get_user_db` dependency to generate our adapter. Notice that we pass it three things:

- A reference to your `UserDB` model.
- The `session` instance we just injected.
- The `UserTable` variable, which is the actual SQLAlchemy model.

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