null = null

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От chester c young
Тема null = null
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Msg-id 20020119163946.8413.qmail@web12708.mail.yahoo.com
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Ответы Re: null = null  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-sql
the following took me by suprise:

egg=# select null=null;?column?
----------t

if this were true, for example, then only one null key could be in a
unique index, which is certainly not true.

i thought the philosphical idea behind null in SQL was you didn't know,
which can't have equivalence (as versus the pragmatic idea in C where
null is a dead end pointer, which can have equivalence).  or have I
been too involved with my Oracle databases?


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