数据库相关
Easy
175. Combine Two Tables
https://leetcode.com/problems/combine-two-tables/#/description
select p.FirstName, p.LastName, a.City, a.State
from Person p left outer join Address a
on p.PersonId=a.PersonId;
176.Second Highest Salary
https://leetcode.com/problems/second-highest-salary/#/description
SELECT MAX(Salary) as SecondHighestSalary
from Employee
where Salary <
(select Max(Salary) from Employee);
181.Employees Earning More Than Their Managers
https://leetcode.com/problems/employees-earning-more-than-their-managers/#/description
SELECT T1.NAME as Employee
FROM Employee T1 INNER JOIN Employee T2
ON T1.ManagerId=T2.Id AND T1.Salary>T2.Salary;
182.Duplicate Emails
https://leetcode.com/problems/duplicate-emails/#/description
select Email from Person group by Email having count(Email) >1;
183.Customers Who Never Order
https://leetcode.com/problems/customers-who-never-order/#/description
select c.Name 'Customers'
from Customers c left join Orders o
on c.Id = o.CustomerId
where o.CustomerId is null;
196.Delete Duplicate Emails
https://leetcode.com/problems/delete-duplicate-emails/#/description
delete p1 from Person p1 inner join Person p2
where p1.Email = p2.Email
and p1.Id>p2.Id;
197.Rising Temperature
https://leetcode.com/problems/rising-temperature/#/description
select t2.Id
from Weather t1 inner join Weather t2
on t1.Temperature <t2.Temperature
and to_days(t1.Date) = to_days(t2.Date)-1 ;
595.Big Countries
select name ,population,area from World where area>3000000 or population>25000000;
596.Classes More Than 5 Students
https://leetcode-cn.com/problems/classes-more-than-5-students/description/
SELECT class from courses group by class having count(distinct student) >= 5;
620.Not Boring Movies
https://leetcode-cn.com/problems/not-boring-movies/description/
select * from cinema where id%2=1 and description <>'boring' order by rating desc;
627.Swap Salary
update salary set sex = if(sex = 'm', 'f','m');
