Re: Null in the where-clause

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От Gregory Seidman
Тема Re: Null in the where-clause
Дата
Msg-id 20020708213340.GA6917@cs.brown.edu
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Ответ на Null in the where-clause  (michael_walzl@yahoo.de (Michael Walzl))
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Michael Walzl sez:
} Hello everybody,
}
} I've got a problem with the "null"-statement within the where-clause.
} I installed the postgres-server 7.2.1 on a Suse Linux machine.
} Then I imported an existing databasedump.
} But when I make the following query:
} select * from tbl_categories where categoryid=null;
} I get 0 rows as result, but there are several records, which
} corrsponds to my query.
} What could be the problem? Do I have to reinstall the server
} with a special parameter?

The problem is that null isn't equal to anything, including itself. While a
null value in a column is not equal to null, it IS NULL:

select * from tbl_categories where categoryid is null;

} Thanx in advance
} Michael Walzl
--Greg




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