leetcode

select name, population, area
from World
where area > 3000000 or population > 25000000;

Select distinct a.Email
from Person a, Person b
where a.Email = b.Email and a.Id != b.Id

select p.FirstName, p.LastName, a.City, a.State
from Person p left join Address a
on p.PersonId=a.PersonId;

select a.Name
from Employee a, Employee b
where a.Salary > b.Salary and a.ManagerId = b.Id

select Customers.Name as Customers
from Customers
where Customers.Id not in (select CustomerId from Orders)

select Score, (select count(distinct a.Score) from Scores a where a.Score >= b.Score) as Rank
from Scores b
order by Score desc

select distinct L2.Num as ConsecutiveNums
from Logs L1, Logs L2, Logs L3
where L1.Id = L2.Id-1 and L3.Id = L2.Id+1 and L1.Num = L2.Num and L3.Num = L2.Num

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
    declare m int;
    set m = N-1;
  RETURN (
      select distinct Salary from Employee order by Salary desc limit m, 1     
  );
END