例题：按年薪的高低显示员工的信息和年薪

# 案例一

SELECT

            *,employees.salary*12*(1+IFNULL(employees.commission_pct,0)) 年薪

FROM

            employees

ORDER BY

            employees.salary*12*(1+IFNULL(employees.commission_pct,0)) DESC;

# 案例二

SELECT

            *,employees.salary*12*(1+IFNULL(employees.commission_pct,0)) 年薪

FROM

            employees

ORDER BY

            年薪 DESC;

  ORDER BY 也支持别名