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Asked: 2026-05-23T14:30:40+00:00

In the documentation of sqlalchemy I read: class sqlalchemy.types.Boolean(create_constraint=True, name=None) A bool datatype. Boolean

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In the documentation of sqlalchemy I read:

class sqlalchemy.types.Boolean(create_constraint=True, name=None)

A bool datatype.

Boolean typically uses BOOLEAN or
SMALLINT on the DDL side, and on the
Python side deals in True or False.

Parameters: create_constraint –
defaults to True. If the boolean is
generated as an int/smallint, also
create a CHECK constraint on the table
that ensures 1 or 0 as a value. name –
if a CHECK constraint is generated,
specify the name of the constraint.

I want to use this type in a declarative way, but I want to understand the parameter descripton first. What is meant by create_constraint and name and what do they do? English is not my natural tong and my knowledge about databases is limited, so thanks for any hints.

What I need is something like:

query_status = Column(Boolean, default = False) # Hope the syntax for default value is correct.

What would this mean:

query_status = Column(Boolean, default = False, create_constraint=True, name='some_name')
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1 Answer

  1. Editorial Team

    query_status = Column(Boolean, default = False) # Hope the syntax for default value is correct.

    yep

    create_constraint = If the boolean is generated as an int/smallint, also create a CHECK constraint on the table that ensures 1 or 0 as a value

    it deals on the database level (DDL). It creates a check constraint to make sure the value stays as int/smallint if it ‘s generated as a int/smallint in the database

    the name argument is the name for that check constraint.

    Well, Im just rephrasing the definition. I hope you understand

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