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Date: Wed, 15 Aug 2007 12:23:58 -0700 (PDT)
From: Richard Broersma Jr <rabroersma@yahoo.com>
Subject: Re: Boolean without default declared
To: Jon Collette <jon@etelos.com>, pgsql-sql@postgresql.org
In-Reply-To: <46C349EA.5050201@etelos.com>
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Message-ID: <775216.56005.qm@web31807.mail.mud.yahoo.com>


--- Jon Collette <jon@etelos.com> wrote:

> If a column with a boolean datatype doesn't have a default value.  What 
> type of value is set if nothing is inserted into that column?  Here is 
> my test table and the queries I have tried.  I can't seem to be able to 
> select the rows where happy has no value.
> 
> *select * from users where happy = '';*
> ERROR:  invalid input syntax for type boolean: ""

Databases have three value logic in it expressions.

is the expression true,
is the expression false,
is the expreassion unknown i.e. null.

SELECT * FROM users WHERE happy IS NULL;

UPDATE users SET happy = false WHERE happy IS NULL;

ALTER TABLE USER ALTER COLUMN happy SET NOT NULL;

Regards,
Richard Broersma Jr.