1、 第二高的薪水
select ifnull((select distinct Salary from Employee order by Salary desc limit 1,1),null) as SecondHighestSalary;
2、第N高的薪水
select distinct Salary from Employee e where N = (select count(distinct Salary) from Employee where Salary >= e.Salary );
3、分数排名
select Score,(select count(distinct score) from Scores where score >= s.score) as Rank from Scores as s order by Score desc;
4、超过经理收入的员工
select e1.Name as Employee from Employee as e1,Employee as e2 where e1.ManagerId=e2.Id and e1.Salary>e2.Salary;
5、 查找重复的电子邮箱
select Email from Person group by Email having count(Email)>1;
6、从不订购的客户
select c.Name as Customers from Customers as c left join Orders as o on c.Id = o.CustomerId where c.Id not in (select c.Id from Customers as c,Orders as o where c.Id = o.CustomerId);
7、部门工资最高的员工
select d.Name as Department,e.Name as Employee,e.Salary from Department as d inner join Employee as e on d.Id = e.DepartmentId and e.Salary>=(select max(Salary) from Employee where DepartmentId=d.Id);
8、删除重复的电子邮箱
delete p1.* from Person p1,Person p2 where p1.Email=p2.Email and p1.id>p2.id;
9、上升的温度
select w1.Id from Weather w1 join Weather w2 on DATEDIFF(w1.RecordDate, w2.RecordDate) = 1 where w1.Temperature>w2.Temperature;
10、交换性别
update salary set
sex = case sex
when 'm' then 'f'
else 'm'
end;