mysql计算两行的某个数值的和

计算相邻两行的年龄的差距

表中的数据如下

select (s.age-(select age from stu where id - s.id = 1)) from stu as s;

select a.age-b.age from stu a,stu b where a.id-b.id=1;

select a.age-b.age from stu a inner join stu b on a.id = b.id + 1;