From: "Bill" <bchie@opensys.com.hk>
Subject: Re: DateDiff, IsNull?
Date: Wed, 15 Aug 2001 11:44:27 +0800
Organization: Hub.Org Networking Services (http://www.hub.org)
Lines: 40
Message-ID: <9lcrij$15lk$2@news.tht.net>
References: <9lb25o$psq$1@news.tht.net>
	<Pine.WNT.4.33.0108140634400.1680-100000@CX1198465-B>
To: pgsql-sql@postgresql.org

IsNull work like this

SELECT IsNull( user_name, '') FROM user ;

then the query will return empty string when the field user_name is null

Regards
Bill

> > Hello all,
> >
> >   I am a newbie to postgreSQL, is it possible to write a "DateDiff",
> > "IsNull" function work same as the one in SQL Server and are there and
> > sample out there? And is it possible to override the existing function
and
> > operator like "+" to become a concate?
>
> I don't know what IsNull does but:
>
> template1=> select coalesce(NULL, 'Hello');
>  case
> -------
>  Hello
> (1 row)
>
> I do know what DateDiff does:
>
> template1=> select '2001-08-14'::date - '6 weeks'::interval;
>         ?column?
> ------------------------
>  2001-07-03 00:00:00-05
> (1 row)
>
> Overloading operators? *Please* tell me that this is impossible.
>
> Alan Gutierrez