依据字串排序
select ename, job
from emp
order by substr(job,length(job)-2, 2)
依据数值排序
select ename, sal
from emp
order by sal
依据数值排序，并限制结果集的行数
select ename, sal
from emp
order by sal
limit 5
对含有字母和数字的字段进行排序
-- order by ename 本质上是提取字符串
select data from
(select ename || '' || deptno as data
from emp) emp
order by replace(translate(data,'0123456789','##########), '#’', '')
排序时对null的处理
select ename, sal, comm
from (select ename, sal, comm, case when comm is null then 0 else comm end as is_null
from emp) x
order by is_null desc, comm
动态调整排序项
select ename, sal, comm
from emp
order by case when job = 'salesman' then comm else sal end
