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On 01/28/07 10:43, A. Kretschmer wrote:
> am Sun, dem 28.01.2007, um 10:25:33 -0600 mailte Ron Johnson folgendes:
>> Hi.
>>
>> These fields do not use any disk space, as the data in them is
>> derived on the fly.
>>
>> For example:
>> CREATE TABLE T_EXAMPLE (
>> SOME_DATE DATE,
>> JDATE COMPUTED BY EXTRACT(JULIAN FROM SOME_DATE)
>> );
>>
>> A work-around is to create a function, and reference it in every
>> query, but storing them in the table definition is the "tidy",
>> low-maintenance way to do it.
>
> Was this a question how to do this in PostgreSQL?
>
> You can use a VIEW. Just create T_EXAMPLE ( SOME_DATE DATE );
> and then
>
> CREATE VIEW view_example AS SELECT some_date, EXTRACT(JULIAN FROM
> some_date) AS julian_date FROM T_EXAMPLE;
Good point.
But then you have 2 bits of metadata, and yet one more object to
update when you add a column.
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