Обсуждение: Problem with FOR SELECT in plpgsql function

I have a problem with the following function:

CREATE OR REPLACE FUNCTION "weiterbildung"."f_termine_uhrzeit" (integer)
RETURNS text AS'
DECLARE      id ALIAS for $1;      dat RECORD;      uhrzeiten text;
BEGIN    uhrzeiten = '''';        FOR dat IN SELECT vormittag_a, vormittag_e, nachmittag_a, nachmittag_e
FROM weiterbildung.t_termine where id_kurs = id order by datum    LOOP        uhrzeiten :=
uhrzeiten||to_char(dat.vormittag_a,''HH24:MI'')||''(''||to_char(dat.vormitta
g_a,''HH24:MI'')||''-''||to_char(dat.vormittag_e,''HH24:MI'')||''
''||to_char(dat.nachmittag_a,''HH24:MI'')||''-''||to_char(dat.nachmittag_e,'
'HH24:MI'')||'')'';    END LOOP;
    RETURN uhrzeiten;
END;
'LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;


This function sometimes returns null even if there is a record in the
database for the corrisponding id.
This happens only when there is only one record for the corrisponding id
value in the database, if there
are more than one record it works with no problem.

Is there a bug in the FOR SELECT statement?

Thanks for advice

On Friday 20 February 2004 10:07, Plant Thomas wrote:
> I have a problem with the following function:
[snip]
>
> This function sometimes returns null even if there is a record in the
> database for the corrisponding id.
> This happens only when there is only one record for the corrisponding id
> value in the database, if there
> are more than one record it works with no problem.

If it actually returns NULL and not the empty string, then the loop must be 
processed, since you set "uhrzeiten" to the empty string before the loop.

Two things to check:
1. None of your variables match a column in your select (and you seem OK 
here).
2. None of the fields in your expression are null (e.g. dat.vormittag_a)

I think it's #2 - concat NULL to any string and you get NULL back.


--  Richard Huxton Archonet Ltd