How can I update only specific fields of a SQLModel object?

[we4r]

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Example Code

from sqlmodel import SQLModel

class HeroUpdate(SQLModel):
    name: str | None = None
    age: int | None = None

update = HeroUpdate(name="Spider-Man")
update_data = update.model_dump(exclude_unset=True)

print(update_data)

Description

I'm working on a FastAPI project using SQLModel and I'm trying to implement a PATCH endpoint.

I want to update only the fields provided in the request without overwriting the existing values with defaults or None.

What is the recommended way to do this using SQLModel?

Is model_dump(exclude_unset=True) the correct approach, or is there a better alternative?

Operating System

Windows

Operating System Details

windows 11

Project Version

not sure

Python Version

3.14.8

Additional Context

No response

[excised]

Yes, model_dump(exclude_unset=True) is the recommended approach for implementing partial updates with SQLModel.

You can combine it with sqlmodel_update():

@app.patch("/heroes/{hero_id}")
def update_hero(
    hero_id: int,
    hero_update: HeroUpdate,
    session: Session = Depends(get_session)
):
    db_hero = session.get(Hero, hero_id)

    if not db_hero:
        raise HTTPException(status_code=404, detail="Hero not found")

    update_data = hero_update.model_dump(exclude_unset=True)

    db_hero.sqlmodel_update(update_data)

    session.add(db_hero)
    session.commit()
    session.refresh(db_hero)

    return db_hero

exclude_unset=True ensures that only fields explicitly provided by the client are included in the update.

This means existing database values remain unchanged when a field is omitted from the PATCH request.

If a field is explicitly provided as None, it will still be included, which is useful when you want to allow nullable fields to be cleared.