Can I create a variable that is not a column in a table but is a field in a model?

[recsater]

First Check

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• I already read and followed all the tutorial in the docs and didn't find an answer.
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• I already checked if it is not related to SQLModel but to SQLAlchemy.

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Example Code

class Test(SQLModel, table=True):
    id: str = Field(primary_key=True) # This is table column.
    age: int = ?? # this is not table column, but can be serialized with functions like model_dump_json.

I also tried https://sqlmodel.tiangolo.com/tutorial/fastapi/multiple-models/#multiple-models-with-inheritance

class HeroBase(SQLModel):
    name: str = Field(primary_key=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)
class Hero(HeroBase, table=True):
    id: int | None = Field(default=None)

class HeroUpdate(HeroBase):
    pass # name, secret_name can be None. but HeroUpdate() raises validation error.

Description

I'd like to retrieve data from a database and provide additional fields to the user. How can I achieve this?

thank you.

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.14

Python Version

3.11.6

Additional Context

And I tried PrivateAttr as well, but that doesn't serialize either.

[wangxin688]

seems it's not support hybrid_property or colunm_property in sqlmodel yet. I guess that's you want in sqlalchemy.

[PipeKnight]

Well, I'm using column_property with SQLModel without any issues. Like this:

QuestionPool.questions_count = column_property(
    select(func.count(LinkPoolQuestion.question_version_id))
    .where(LinkPoolQuestion.question_pool_id == QuestionPool.id)
    .correlate(QuestionPool)
    .scalar_subquery(),
)

[PipeKnight]

I checked and hybrid_property could be used in the same way. Described here:
#299 (comment)

[Jijun-TANG]

@PipeKnight Thanks so much for the reply, it helps a lot!

[PipeKnight]

See my reply here: #729 (reply in thread)
Both column_property and hybrid_property are supported is you're using them straight-forward and not like decorators

[recsater]

I still can't create a serializable variable that isn't a column in a table.