Обсуждение: Dumb question: How do I determine programmatically if a column is nullable?

Dann Corbit wrote:

> What API call can I make to find out if a column is nullable or not?
>  

SELECT attnotnull FROM pg_attribute ...
see documentation "Internals/System Catalogs"

Regards,
Andreas

> -----Original Message-----
> From: Andreas Pflug [mailto:pgadmin@pse-consulting.de]
> Sent: Wednesday, January 07, 2004 11:17 AM
> To: Dann Corbit
> Cc: pgsql-hackers@postgresql.org
> Subject: Re: [HACKERS] Dumb question: How do I determine
> programmatically if a column is nullable?
>
>
> Dann Corbit wrote:
>
> > What API call can I make to find out if a column is nullable or not?
> >
>
> SELECT attnotnull FROM pg_attribute ...
> see documentation "Internals/System Catalogs"

Is there a way do do it when I have some arbitrary query that returns a
result set?

In other words, I will be passed a SQL query.  I don't want to have to
parse it myself.

Rather, I want to know (for the bound columns) if a column is nullable
or not.

Is the functionality available in [for example] libpq?

"Dann Corbit" <DCorbit@connx.com> writes:
> In other words, I will be passed a SQL query.  I don't want to have to
> parse it myself.
> Rather, I want to know (for the bound columns) if a column is nullable
> or not.
> Is the functionality available in [for example] libpq?

As of 7.4, see PQftable() and PQftablecol(), and look into pg_attribute
to see whether the column is marked NOTNULL.
        regards, tom lane