Re: Empty String Comparison Standard compliant?

Поиск
Список
Период
Сортировка
От Tom Lane
Тема Re: Empty String Comparison Standard compliant?
Дата
Msg-id 13485.1075475931@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Empty String Comparison Standard compliant?  (Christoph Haller <ch@rodos.fzk.de>)
Список pgsql-sql
Christoph Haller <ch@rodos.fzk.de> writes:
> [ '' is less than 'GDMF' ]

> Are these results standard compliant? 

I doubt that the SQL standard really says anything on the subject, but
ISTM any rational string-sorting algorithm would put '' before anything
else.

> It's just because I have a DBMS here, where the results are vice versa. 

Let me guess ... it's Oracle?  Last I heard Oracle had a problem
distinguishing empty strings from NULLs.  If it sorts NULLs at the
end then it wouldn't be surprising for empty strings to come out at
the end in an ORDER BY sort.  However, I'm not sure that explains
the exact example you cite of boolean comparison results.  If it
were taking the '' as a NULL then both comparisons ought to return
NULL.
        regards, tom lane


В списке pgsql-sql по дате отправления:

Предыдущее
От: Christoph Haller
Дата:
Сообщение: Empty String Comparison Standard compliant?
Следующее
От: Stephan Szabo
Дата:
Сообщение: Re: Empty String Comparison Standard compliant?