mysql:生年月日から年齢を求める

SET @birthday = '1980-01-12', @now = '2020-01-12' ;

SELECT (YEAR(DATE(@now)) - YEAR( @birthday )) 
  - (RIGHT(@birthday, 5) > RIGHT(DATE(@now), 5)) AS age;

SET @birthday = '1980-01-12';

SELECT (YEAR(DATE(NOW())) - YEAR( @birthday )) 
  - (RIGHT(@birthday, 5) > RIGHT(DATE(NOW()), 5)) AS age;