Re: "Named" column default expression

Thom Brown, 28.10.2011 10:10:
> On 28 October 2011 08:29, Thomas Kellerer<spam_eater@gmx.net>  wrote:
>> Hello,
>>
>> I just noticed that Postgres allows the following syntax:
>>
>> create table foo
>> (
>>     id integer constraint id_default_value default 42
>> );
>>
>> But as far as I can tell the "constraint id_default_value" part seems to be
>> only syntactical sugar as this is stored nowhere. At least I couldn't find
>> it going through the catalog tables and neither pg_dump -s or pgAdmin are
>> showing that name in the generated SQL source for the table.
>>
>> It's not important, I'm just curious why the syntax is accepted (I never saw
>> a default value as a constraint) and if there is a way to retrieve that
>> information once the table is created.
>
> It would do something with it if you actually defined a constraint
> after it, but since you didn't, it throws it away since there's
> nothing to enforce.  So if you adjust it to:
>
> create table foo
> (
>     id integer constraint id_default_value check (id>  4) default 42
> );
>
> a constraint for that column will be created with the specified name.

Thanks, makes somewhat sense.

I'm wondering why this doesn't throw an error then.

Regards
Thomas