Age in years
Given a birthdate in @dob, here is a simple formula for age in years:
DATE_FORMAT(FROM_DAYS(TO_DAYS(now()) - TO_DAYS(@dob)), '%Y') + 0;
and here is one for age in years to two decimal places (ignoring day of month):
ROUND((((YEAR(now()) - YEAR(@dob)))*12 + (((MONTH(now()) - MONTH(@dob)))))/12, 2)