Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards

Поиск
Список
Период
Сортировка
От Tom Ivar Helbekkmo
Тема Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards
Дата
Msg-id 86ofs0m3vj.fsf@athene.i.eunet.no
обсуждение исходный текст
Ответ на AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards  (Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at>)
Список pgsql-hackers
Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:

> Actually I am not sure whether the column = NULL syntax is even
> defined or allowed in SQL92

I've just checked, by reading the relevant paragraphs and studying the
BNF, and the standard says that any comparison of the form X <comp op>
Y is unknown if X or Y (or both) is NULL, including the case where
NULL is given as an explicit constant.  So, SQL92 clearly demands that
"column = NULL" is UNKNOWN, never TRUE or FALSE.

-tih
-- 
The basic difference is this: hackers build things, crackers break them.


В списке pgsql-hackers по дате отправления:

Предыдущее
От: Bruce Momjian
Дата:
Сообщение: Re: Re: 7.2 items
Следующее
От: Stephan Szabo
Дата:
Сообщение: Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards