Question

I have a user table with the user’s birthday (YYYY-MM-DD) as well as age. I want to run a script to calculate and update the age column nightly via cron.

This SQL works well for selecting and calculating the age:

SELECT 
    DATE_FORMAT(NOW(), '%Y') - 
    DATE_FORMAT(`birthday`, '%Y') - 
    (DATE_FORMAT(NOW(), '00-%m-%d') < DATE_FORMAT(`birthday`, '00-%m-%d')) AS age
FROM 
    `jos_jcourse_students`

But is it possible to update the age column with a single statement? Tried the following, but all I managed to do was populate the age column with all 0s! Do I need to use some sort of MySQL loop?

UPDATE 
    `jos_jcourse_students` 
SET 
    age = "SELECT DATE_FORMAT(NOW(), '%Y') - 
    DATE_FORMAT(`birthday`, '%Y') - 
    (DATE_FORMAT(NOW(), '00-%m-%d') < DATE_FORMAT(`birthday`, '00-%m-%d')) AS age
FROM 
    `jos_jcourse_students`"

Answer 1

UPDATE `jos_jcourse_students` 
SET age = DATE_FORMAT(FROM_DAYS(TO_DAYS(NOW())-TO_DAYS(birthday)), '%Y')+0 

OR according to your logic it will be

UPDATE `jos_jcourse_students` 
SET age =((DATE_FORMAT(NOW(), '%Y') - DATE_FORMAT(`birthday`, '%Y')) - 
    (DATE_FORMAT(NOW(), '00-%m-%d') < DATE_FORMAT(`birthday`, '00-%m-%d')))