| From: | Dimitri Fontaine <dfontaine(at)hi-media(dot)com> |
|---|---|
| To: | Durumdara <durumdara(at)gmail(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: "= Null" <> "is Null"? |
| Date: | 2009-07-08 12:45:21 |
| Message-ID: | 87fxd7baxq.fsf@hi-media-techno.com |
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| Lists: | pgsql-general |
Durumdara <durumdara(at)gmail(dot)com> writes:
> Some of other DBs are uses Null as Null in >=< comparisons. Is PG not?
> What are the rules?
PostgreSQL implements SQL, which has a 3-valued logic. There's True,
there's False, and there's NULL. NULL means that we know nothing about
what's in there.
Would you really want to say that something you know nothing about is
the same thing as this other thing you know nothing about?
In PostgreSQL, NULL = NULL answers NULL (we know nothing about the
result).
Regards,
--
dim
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