ge and le for Field should create CheckConstraint

[throwable-one]

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Example Code

from sqlalchemy import Column, Integer, CheckConstraint, create_engine
from sqlmodel import SQLModel, Field, Session


class UserWithSQLModel(SQLModel, table=True):
    id: int | None = Field(primary_key=True)
    age: int = Field(le=100, ge=18, nullable=False)


class UserWithConstraint(SQLModel, table=True):
    id: int | None = Field(primary_key=True)
    age: int = Field(sa_column=Column(Integer, CheckConstraint("age < 100 AND age > 18")))


if __name__ == "__main__":
    engine = create_engine("sqlite://")
    SQLModel.metadata.create_all(engine)
    with Session(engine) as session:
        user = UserWithSQLModel(age=200)
        # Uncomment this line to see it fails
        # user = UserWithConstraint(age=200)
        session.add(user)
        session.commit()

Description

For Integer field I already set limits using ge and le. It would be nice to have it as a constraint also.

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.31

Python Version

3.14

Additional Context

No response

[apoorva-01]

ge/le are Pydantic validators, so they only run in Python when you construct the object. They never turn into DDL, which is why your age=200 row saves fine when it reaches the database by some other path.

If you want the database to enforce it too, add the check with __table_args__. You don't need sa_column for this, the constraint just references the column by name:

from sqlalchemy import CheckConstraint
from sqlmodel import SQLModel, Field


class UserWithSQLModel(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    age: int = Field(ge=18, le=100, nullable=False)

    __table_args__ = (
        CheckConstraint("age >= 18 AND age <= 100", name="ck_age_range"),
    )

Now you get both layers: ge/le fails early in Python with a clean validation error, and the CheckConstraint catches anything that skips validation (raw SQL, a bulk insert, a different client).

Auto-generating the constraint from ge/le would be nice, but it's a real feature rather than a bug, since the SQLAlchemy side has no idea about the Pydantic validators. For now __table_args__ is the way.