Thank you for your response.
Yes I know that i can make a function.
Is there a way to do this transparently I want to treat this function as a field in the table.
The reason why i want to do that is because i have a class that has generic method to retrieve data.
It receives list of field names and returns their values from the table.
If I want to implement the function method i will have to modify the class method and will have to treat specially the
retrieve fullname thing.
Holger Krug wrote:
On Thu, Jan 10, 2002 at 11:50:08AM +0200, Roman Gavrilov wrote:
> Suppose that I have a table with 3 fields name, version, release.
> name | version | release
> ------------------
> test | 1 | 2
> ema | 1.2 | 2.2
> ------------------
>
> I want to retrieve full name as 'select name || '-' || version || '-'
> release from table';
> test-1-2
> ema-1.2-2.2
>
> I can do this as regular sql query;
> But i would like to do this as 'select full_name from table'
>
> One way is to create view which will do the job.
> Other way to do this is to create additional field name full_name and to
> store the full name inside the field.
> Is there any possibility to create function or constraint trigger that
> will know that when I am doing select full_name it should
> concat name version release and return it as full_name.(full_name is
> virtual field) Not a trigger, triggers work only ON UPDATE and ON INSERT but not ON SELECT.
> I don't want to create it as view;
That's they way how PostgreSQL does this kind of work. Why not ?
Alternatively you can use a function:
SELECT fullname(table) FROM table;
Here's the function definition:
CREATE OR REPLACE FUNCTION fullname(table)
RETURNS text AS
'BEGIN
RETURN $1.name || ''-'' || $1.version || ''-'' $1.release;
END'
LANGUAGE plpgsql;
The syntax of the CREATE FUNCTION statement as given here is valid for
PostgreSQL 7.2, former versions have a slightly different syntax. See the
command reference page for CREATE FUNCTION.
Good luck !
--
Holger Krug
hkrug@rationalizer.com
--
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Roman Gavrilov
Aduva Inc., Web Development Services.
work +972-3-7534324 mobile +972-54-834668
romio@aduva.com, romio@netvision.net.il
