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Re: comparing null value in plpgsql.

From: Bhuvan A <bhuvansql(at)yahoo(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: Re: comparing null value in plpgsql.
Date: 2002-03-11 07:21:19
Message-ID: Pine.LNX.4.20.0203111249510.31041-100000@Larry (view raw or flat)
Thread:
Lists: pgsql-bugs

On Mar 10, Stephan Szabo wrote:

> On Mon, 11 Mar 2002, Bhuvan A wrote:
> 
> > here i have a problem in comparing null values in plpgsql. this exist
> > in 7.1.x and 7.2 as well.
> >
> > the condition <null value> != <valid value> fails in plpgsql.
> > consider this function is triggered on every updation on a table.
> >
> >   create function ftest()
> >   returns opaque as 'declare
> >
> >   begin
> >
> >     if new.comp_code != old.comp_code then
> >       ...
> >     end if;
> >     return new;
> >   end;'
> >   language 'plpgsql';
> >
> > this condition fails if old.comp_code is null and new.comp_code has
> > some value.
> 
> <nullvalue> != <anything> is not true, it's unknown, so the if shouldn't

  what do you mean by <nullvalue> != <anything>?

> fire.  It's a side effect of how the spec defines operations on nulls.
> 

here i mean..

if <nullvalue> != <not null value>, the loop is not fired, but else loop is
getting fired. why?

Regards,
Bhuvaneswaran.



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