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Re: isnull

From: Joseph Shraibman <jks(at)p1(dot)selectacast(dot)net>
To: jhunt(at)chac(dot)qld(dot)edu(dot)au
Cc: Joseph Shraibman <jks(at)p1(dot)selectacast(dot)net>, "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org>
Subject: Re: isnull
Date: 2000-03-30 23:07:16
Message-ID: 38E3DE24.72ACFA25@selectacast.net (view raw or flat)
Thread:
Lists: pgsql-sql
Julie Hunt wrote:

> Yes, you're right.  I remember attempting to do an outer left join using the
> nullif but without success so I used the case function instead with success.
> Maybe someone else knows more about nullif and why it doesn't seem to work.
>
> Regards,
> Julie
>

I've actually taken a closer look at the web page and not only did the name change,
but I now notice that they change what it is supposed to do as well.  It does work
as currently defined, but I needed something that does what the original
documentation said:

IFNULL(input,non-NULL substitute)
 return second argument if first is NULL
 Example:        IFNULL(c1, 'N/A')


>
> Joseph Shraibman wrote:
>
> > Julie Hunt wrote:
> >
> > > Sorry, I haven't come across ifnull
> >
> > Ah, I think the documentation that came with 6.5.3 was wrong, because
> > http://www.postgresql.org/docs/postgres/functions.htm#AEN2257 has the function
> > nullif  where ifnull was in my documentation.  I don't get errors now, but it
> > just doesn't seem to do it's job.
> >
> > playpen=> insert into tablea values (100, null);
> > INSERT 23168 1
> > playpen=> select * from tablea;
> > indexa|data
> > ------+----
> >      1|   1
> >      2|   2
> >      3|   2
> >      4|   4
> >      7|   7
> >      6|   8
> >      5|   8
> >    100|
> > (8 rows)
> >
> > playpen=> select *, data from tablea;
> > indexa|data|data
> > ------+----+----
> >      1|   1|   1
> >      2|   2|   2
> >      3|   2|   2
> >      4|   4|   4
> >      7|   7|   7
> >      6|   8|   8
> >      5|   8|   8
> >    100|    |
> > (8 rows)
> >
> > playpen=> select *, nullif(data, 9) from tablea;
> > indexa|data|case
> > ------+----+----
> >      1|   1|   1
> >      2|   2|   2
> >      3|   2|   2
> >      4|   4|   4
> >      7|   7|   7
> >      6|   8|   8
> >      5|   8|   8
> >    100|    |
> > (8 rows)
> >
> > >
> > > Julie
> > >
> > > >Oops, my mistake.  I meant ifnull.  Whenever I try to use ifnull I get an
> > > >error so I have to use a case when a = null then default else a end.
> > > >
> > > >Julie Hunt wrote:
> > > >
> > > >> There is a space between is and null: is null
> > > >>
> > > >> Regards
> > > >>
> > > >> Joseph Shraibman wrote:
> > > >>
> > > >> > Could someone give me an example of isnull?  Whenever I try it I get an
> > > >> > error message.
> > > >


In response to

  • Re: isnull at 2000-03-30 22:58:32 from Julie Hunt

Responses

  • Re: isnull at 2000-03-31 01:10:42 from Julie Hunt
  • Re: isnull at 2000-03-31 01:43:00 from Bruce Momjian

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Subject: Re: isnull
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Subject: Re: removing a field from a table

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