Re: postgresql vs mysql

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От brian
Тема Re: postgresql vs mysql
Дата
Msg-id 45DD276F.5040909@zijn-digital.com
обсуждение исходный текст
Ответ на Re: postgresql vs mysql  (Chris <dmagick@gmail.com>)
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Chris wrote:
>
> It's not an oddity.
>
> An empty string is a KNOWN value. You know exactly what that value is -
> it's an empty string.
>
> A NULL is UNKNOWN - it doesn't have a value at all.
>

Just to expand on that (and to drag this thread out a little longer), i
find that a pretty good way to get across this difference is to refer to
it as *the* empty string. I prefer this description because it is
implicit that it is still a string. NULL has no type, regardless of the
column it is inserted into. Thus, the empty string is NOT NULL.

brian

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