mysql语法难点

select * from emp where comm is null or comm=0;/*没有提成的员工*/

查询有提成的员工所有信息

select * from emp where comm is not null and comm>0;/*有提成的员工*/

找出有奖金的员工的不同工作,不要重复数据

select distinct job from emp where comm is not null and comm>