| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | Erik Jones <ejones(at)engineyard(dot)com> |
| Cc: | Waldemar Bergstreiser <littlesuspense(at)web(dot)de>, Greg Stark <gsstark(at)mit(dot)edu>, pgsql-general(at)postgresql(dot)org, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Subject: | Re: |
| Date: | 2009-06-30 18:42:26 |
| Message-ID: | b42b73150906301142m316fb5auf0065573b6cf03c8@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-general |
On Tue, Jun 30, 2009 at 1:22 PM, Erik Jones<ejones(at)engineyard(dot)com> wrote:
>> and if I have a row in table C where c.id is null? A don't know.
>
> No, it's perfectly clear as 'NULL = NULL' evaluates to false:
>
> postgres=# select null = null;
> ?column?
> ----------
>
you can test for that with 'is distinct from':
select null is distinct from null; -- false
select null is distinct from 1; -- true
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