Re: how to sort a birthday list ?

Bruno Wolff III wrote:
>
> On Fri, Jun 21, 2002 at 10:30:54 +0200,
> Michael Agbaglo <byteshifter(at)shifted-bytes(dot)de> wrote:
> >
> > of course you could sort by DOY but then you'll have a problem w/ the
> > next year:
> >
> > if it's let's say december and you select the list for the next 60 days,
> > persons having birthday in december will appear after persons having
> > birthday in january.
> >
> > I tried to use CASE WHEN... THEN in ORDER BY but it doesn't seem to work
> > (syntax error at '')
>
> You also need to worry about leap years. If a birthday is February 29
> and there isn't one this year, what do you want to happen?

You can create a little PL/pgSQL function like this:

CREATE FUNCTION next_birthday(date) RETURNS date AS '
DECLARE
p_dob ALIAS FOR $1;
v_age integer;
v_birthday date;
BEGIN
-- First we get the age in years
v_age := EXTRACT (YEAR FROM CURRENT_DATE) -
EXTRACT (YEAR FROM p_dob);

-- We add that to the DOB to get this years birthday
v_birthday := p_dob + (v_age::text || '' years'')::interval;

-- If that is in the past, we add another year
IF v_birthday < CURRENT_DATE THEN
v_birthday := v_birthday + ''1 year''::interval;
END IF;

RETURN v_birthday;
END;'
LANGUAGE plpgsql;

It just calculates the next birthday of a person relative from today.
Then query with

SELECT next_birthday(birthday), name
FROM person ORDER BY 1;

Jan

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