Re: comparing null value in plpgsql.
От | |
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Тема | Re: comparing null value in plpgsql. |
Дата | |
Msg-id | Pine.LNX.4.20.0203111227000.29061-100000@Larry обсуждение исходный текст |
Ответ на | Re: comparing null value in plpgsql. (Stephan Szabo <sszabo@megazone23.bigpanda.com>) |
Список | 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. why?
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