Comments on: A simple way to make birthday queries easier and faster

By: Robert

Robert — Fri, 15 Jan 2010 16:03:23 +0000

I played very long to find a fast solution for querys around the birthdate. Two weeks ago, I wrote about my GETAGE() function, and the first thing I tried to find friends which have birthday in a couple of days was writing a similar function with that body: DATE_ADD(bday, INTERVAL YEAR(FROM_DAYS(DATEDIFF(NOW(), bday) – 1)) + 1 YEAR)

I used this function inside of a trigger and for an update-routine to get a clean column for all of my friends that has birthday in up to one week. This worked for a while, but there are in theory $num_of_users / 365 birthdays per day. With an increasing $num_of_users you also have to update more rows – so I rewrote the system once more. A little intermediate step was using a VARCHAR colum with a REVERSE()’d DATE value to run a LIKE on it. This is also not the best solution because you need more code in the userspace, so I tried a DAY(bday)*100 + MONTH(bday) solution, which is really the best. Especially because you can write a little condition, so that all februry 29 can reduced by 100, if the current year does not have 29 days in that month.

By: depesz

depesz — Fri, 01 Jan 2010 10:42:44 +0000

I once wrote about it, including indexed way to search for people who have birthday “tomorrow” – it is for PostgreSQL, but shows some pitfalls, and possible solutions:
http://www.depesz.com/index.php/2007/10/26/who-has-birthday-tomorrow/

By: Josh Davis

Josh Davis — Thu, 31 Dec 2009 22:21:48 +0000

When reading this entry I was thinking about simply storing the “day of the year” value (0 to 365) but then I realized it could complicate things on leap years. If you store them separately, people born on a 29th of February shouldn’t be a problem with

SELECT *
FROM users
WHERE (birth_month, birth_day) BETWEEN (2, 27) AND (3, 6)

PS: your CAPTCHA is tricky. It asked me if a lion is a cat and it made check Wikipedia wondering if it was a trick question :)