Mike thank you.
I think,
Use __table_args__ This is the definitive usage.
If you can add a sample to the Sqlalchemy documentation.
Let beginners avoid using the wrong method and confused.
Mike Bayer於 2018年3月19日星期一 UTC+8下午9時27分47秒寫道：
>
> On Mon, Mar 19, 2018 at 12:52 AM, lone ois <ois...@gmail.com <javascript:>>
> wrote:
> > Hi!
> > i test sqlalchemy 1.1.12 - 1.2.5
> > create table check constraint.
> > -----------------------------------
> > class testTable(db):
> > __tablename__ = 'testTable'
> >
> > id = Column(INT, primary_key = True, autoincrement = True, unique =
> > True)
> > ser = Column(INT)
> >
> > CheckConstraint('ser>100')
> >
> > #sqlalchemy echo and pgadmin4
> >
> > CREATE TABLE "testTable" (
> > id SERIAL NOT NULL,
> > ser INTEGER,
> > PRIMARY KEY (id),
> > UNIQUE (id)
> >
> > no check constraint.
> > ------------------------------
> > class testTable(db):
> > __tablename__ = 'testTable'
> >
> > id = Column(INT, primary_key = True, autoincrement = True, unique =
> > True)
> > ser = Column(INT)
> > __table_args__ = (
> > CheckConstraint('ser>100'),
> > )
> >
> >
> > #sqlalchemy echo
> > CREATE TABLE "testTable" (
> > id SERIAL NOT NULL,
> > ser INTEGER,
> > PRIMARY KEY (id),
> > CHECK (ser>100),
> > UNIQUE (id)
> >
> > this OK!
> >
> > so, i must use __table_args__ define CheckConstraint ??
>
> when you add an object to a Python class:
>
> class MyClass(object):
>
> # ....
>
> "hello!"
>
> that string "hello" has no way of being intercepted by the class and
> it knows nothing about it. SQLAlchemy's declarative has no way to see
> this. So with your CheckConstraint example, this suggests that yes,
> you do need to use __table_args__. However, there is an exception,
> which is probably what you discovered, if you make a UniqueConstraint
> or CheckConstraint that refers to the Column objects directly,
> SQLAlchemy figures this out:
>
>
> class MyClass(Base):
> # ...
> foo = Column(...)
> bar = Column(...)
>
> CheckConstraint("foo > bar")
>
> vs.
>
> class MyClass(Base):
> # ...
> foo = Column(...)
> bar = Column(...)
>
> CheckContraint(foo > bar)
>
>
> That said, you should really use __table_args__ for these as that is
> the idiomatic approach and will work consistently in all cases.
>
>
>
>
> >
> >
> >
> >
> >
> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
> > To post example code, please provide an MCVE: Minimal, Complete, and
> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> > description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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