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Thread: Why isn't that null

Why isn't that null

From
Matthias Teege
Date:
Moin,

I have al small problem with ISNULL in a trigger
function. My definition looks like:

IF NEW.vkp ISNULL THEN
   select t1.las into i_kd
   from auftrag t1, aufpos t2 where
   t2.auftrag = t1.id;
   select get_vkp(i_kd, NEW.artikel) into f_vkp;
   NEW.vkp:=f_vkp;
END IF;

The following SQL query didnt cause this if statement:

insert into aufpos(auftrag, artikel, best_menge, vkp,
lieferwoche, cuser, ctime, uuser, utime) values
('175','8501900','12','','3500','matthias',
now (), 'matthias',now ())

If I change the function statement as follows:

IF NEW.vkp = 0 THEN
   ...
END IF;

it works but '0' is a leagal value but not '' (empty). The
function should only be called if NEW.vkp ist empty.

Many thanks
Matthias

Re: Why isn't that null

From
NRonayette
Date:
Hi,

May be this insert will work with your test in your function

insert into aufpos(auftrag, artikel, best_menge, vkp,
 lieferwoche, cuser, ctime, uuser, utime) values
('175','8501900','12',NULL,'3500','matthias',
 now (), 'matthias',now ())

Nicolas

Matthias Teege a écrit :
>
> Moin,
>
> I have al small problem with ISNULL in a trigger
> function. My definition looks like:
>
> IF NEW.vkp ISNULL THEN
>    select t1.las into i_kd
>    from auftrag t1, aufpos t2 where
>    t2.auftrag = t1.id;
>    select get_vkp(i_kd, NEW.artikel) into f_vkp;
>    NEW.vkp:=f_vkp;
> END IF;
>
> The following SQL query didnt cause this if statement:
>
> insert into aufpos(auftrag, artikel, best_menge, vkp,
> lieferwoche, cuser, ctime, uuser, utime) values
> ('175','8501900','12','','3500','matthias',
> now (), 'matthias',now ())
>
> If I change the function statement as follows:
>
> IF NEW.vkp = 0 THEN
>    ...
> END IF;
>
> it works but '0' is a leagal value but not '' (empty). The
> function should only be called if NEW.vkp ist empty.
>
> Many thanks
> Matthias

Re: Why isn't that null

From
Tom Lane
Date:
Matthias Teege <matthias@mteege.de> writes:
> I have al small problem with ISNULL in a trigger
> function. My definition looks like:

> IF NEW.vkp ISNULL THEN
>    ...

> The following SQL query didnt cause this if statement:

> insert into aufpos(auftrag, artikel, best_menge, vkp,
> lieferwoche, cuser, ctime, uuser, utime) values
> ('175','8501900','12','','3500','matthias',
> now (), 'matthias',now ())

This seems correct to me --- an empty string '' is certainly not
the same thing as NULL.

> If I change the function statement as follows:

> IF NEW.vkp = 0 THEN
>    ...
> END IF;

> it works

Shouldn't that give a type error of some sort?  You didn't say
what type vkp is, but if it's a string type then comparing it
against a numeric shouldn't work IMHO.

            regards, tom lane

Re: Why isn't that null

From
Matthias Teege
Date:
Tom Lane <tgl@sss.pgh.pa.us> writes:

[...]

> > If I change the function statement as follows:
>
> > IF NEW.vkp = 0 THEN
> >    ...
> > END IF;
>
> > it works
>
> Shouldn't that give a type error of some sort?  You didn't say
> what type vkp is, but if it's a string type then comparing it
> against a numeric shouldn't work IMHO.

no it isn't. It is a float8 type. I changed my program in
that way that the query includes NULL instead of ''.

Bis dann
Matthias


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Matthias Teege -- matthias@mteege.de -- http://emugs.de
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