1.已知生日，求年龄 TIMESTAMPDIFF(year,birthday,CURDATE()) age 2.根据字段内有无值，判断状态 ISNULL(die_date) status 3.mapper.xml里的date类型与mysql中的日期作比较 and a.diagnosed >= DATE_FORMAT(#{start_diagnosed}, '%Y-%m-%d') and a.diagnosed <= DATE_FORMAT(#{end_diagnosed}, '