题目描述
找出所有员工当前(to_date=‘9999-01-01’)具体的薪水salary情况,对于相同的薪水只显示一次,并按照逆序显示
CREATE TABLE `salaries
` (
`emp_no
` int(11) NOT NULL,
`salary
` int(11) NOT NULL,
`from_date
` date NOT NULL,
`to_date
` date NOT NULL,
PRIMARY KEY (`emp_no
`,`from_date
`));
解答:
去重可以使用distinct去重以及group by分组去重(前面的第2题也有去重)
select distinct salary
from salaries
where to_date
="9999-01-01"
order by salary
desc
select salary
from salaries
where to_date
="9999-01-01"
group by salary
order by salary
desc