使用 SQLAlchemy 或 SQLModel 從 3 個不同的表中獲取數據

Question

我想用 SQLAlchemy 或 SQLModel 從 3 個表中獲取數據。 例如，假設我的表如下：

class A(SQLModel, table=true):
    id: int
    title: str

class B(SQLModel, table=true):
    id: int
    a_id: foreign_key("a.id")
    name: str
 
class C(SQLModel, table=true):
    id: int
    b_id: foreign_key("b.id")
    text: str

我想要的響應如下：

[
    {
        "id": 1,
        "title": "This is A table",
        "b": [
            {
                "id": 1,
                "name": "This is B table",
                "c":[
                   {
                        "id":1,
                        "text": "My text from c" 
                   }               
                ]
            }
        ]
    }
]

我正在嘗試使用 selectinload 但不起作用

query = (
        select(A)
        .where(A.id == a_id)
        .options(
            selectinload(A.b).joinedload(
                B.c
            )
        )
    )

    try:
        response = (await session.exec(query)).one()
    except NoResultFound:
        raise HTTPException(status_code=404, detail="Data not found")

先感謝您

Answer 1

我已經使用較新版本的 sqlalchemy（不是 sqlmodel）嘗試了這些模型，它的工作原理如本示例所示（sqlalchemy = 1.4.39）

class A(Base):
    __tablename__ = 'a'

    id = Column(Integer, primary_key=True)
    title = Column(String(length=100))

    b = relationship("B", backref="a")

class B(Base):
   __tablename__ = 'b'

   id = Column(Integer, primary_key=True)
   name = Column(String(length=100))

   a_id = Column(ForeignKey('a.id', ondelete='CASCADE'))

   c = relationship("C", backref="b")

class C(Base):
   __tablename__ = 'c'

   id = Column(Integer, primary_key=True)
   text = Column(String(length=100))

   b_id = Column(ForeignKey('b.id', ondelete='CASCADE'))

詢問：

stmt = select(A).options(selectinload(A.b).selectinload(B.c))
resp = await session.execute(query)
return resp.scalars().all() 

（准備與此查詢相關的 pydantic model）schema.py

class CResp(BaseModel):
    id: int
    text: str

class BResp(BaseModel):
    id: int
    name: str
    c: List[CResp]

class AResp(BaseModel):
    id: int
    title: str
    b: List[BResp]

視圖.py

@app.get("/", response_model=List[AResp])
async def index(session=Depends(get_session)):
    query = select(A).options(selectinload(A.b).selectinload(B.c))
    resp = await session.execute(query)
    return resp.scalars().all() 

If you want to use this query with sqlmodel, you can try some other versions of sqlalchemy as mentioned here ( SQLModel error: "AttributeError: 'Team' object has no attribute 'heroes'" ), sqlmodel has some problems with SQLalchemy 1.4.36 + 版本