Postgres birthdays selection

Question

I work with a Postgres database. This DB has a table with users, who have a birthdate (date field). Now I want to get all users who have their birthday in the upcoming week.

Answer 1

Here's my take, which works with leap years too:

CREATE OR REPLACE FUNCTION days_until_birthday(
    p_date date
    ) RETURNS integer AS $$
DECLARE
    v_now date;
    v_days integer;
    v_date_upcoming date;

    v_years integer;

BEGIN
    v_now = now()::date;
    IF (p_date IS NULL OR p_date > v_now) THEN
        RETURN NULL;
    END IF;

    v_years = date_part('year', v_now) - date_part('year', p_date);

    v_date_upcoming = p_date + v_years * interval '1 year';

    IF (v_date_upcoming < v_now) THEN
        v_date_upcoming = v_date_upcoming + interval '1 year';
    END IF;

    v_days = v_date_upcoming - v_now;
    RETURN v_days;
END
$$ LANGUAGE plpgsql IMMUTABLE;