How to get an age from a D.O.B field in MySQL?

SELECT DATE_FORMAT(NOW(), '%Y') - DATE_FORMAT(dob, '%Y') - (DATE_FORMAT(NOW(), '00-%m-%d') < DATE_FORMAT(dob, '00-%m-%d')) AS age

Use Mysql recommended :

TIMESTAMPDIFF(YEAR, dob, CURDATE()) AS age;

Usage in a query :

SELECT name, dob, TIMESTAMPDIFF(YEAR, dob, CURDATE()) AS age FROM pet;

Ref: http://dev.mysql.com/doc/refman/5.0/en/date-calculations.html