根据条件取不同列中的值来排序

select empno ,

ename,

case when sal >= 1000 and sal <2000 then 1 else 2 end as 级别

from emp;

排序

select 

empno ,

ename,

sal

from emp order by case when sal >= 1000 and sal <2000 then 1 else 2 end , 3;