What is async SQLAlchemy and when to use it?

Question

Accepted Answer

**Async SQLAlchemy** allows **non-blocking database** operations in FastAPI.

```python
from sqlalchemy.ext.asyncio import (
    create_async_engine,
    AsyncSession,
    async_sessionmaker
)
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

class Base(DeclarativeBase):
    pass

class User(Base):
    __tablename__ = "users"
    id: Mapped[int] = mapped_column(primary_key=True)
    name: Mapped[str]
    email: Mapped[str]

# Engine and session
engine = create_async_engine(
    "postgresql+asyncpg://user:pass@localhost/db",
    echo=True
)

async_session = async_sessionmaker(engine, expire_on_commit=False)

# Dependency
async def get_db():
    async with async_session() as session:
        yield session

# Usage
async def create_user(db: AsyncSession, name: str, email: str):
    user = User(name=name, email=email)
    db.add(user)
    await db.commit()
    return user

async def get_users(db: AsyncSession):
    result = await db.execute(select(User))
    return result.scalars().all()
```

**Drivers:**
- PostgreSQL: `asyncpg`.
- MySQL: `aiomysql`.
- SQLite: `aiosqlite`.

Python: What is async SQLAlchemy and when to use it?