3个月用python刷完leetcode600题!-数据库中等题

算法刷多了，感觉脑子里全是浆糊了，所以做一做数据库的题调整一下，哈哈哈哈！

177. Nth Highest Salary

177. Nth Highest Salary

limit的第一个数的意思是跳过多少记录，第二个数的意思是取多少条记录。不知道这里limit N-1 为何不行。
CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
Declare M INT;
set M=N-1;
RETURN (
# Write your MySQL query statement below.
select distinct Salary from Employee order by Salary desc limit M,1
);
END

178. Rank Scores

178. Rank Scores

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

180. Consecutive Numbers

180. Consecutive Numbers

三表内链接：
select distinct l1.Num as ConsecutiveNums from Logs as l1,Logs as l2,Logs as l3 where l1.Id + 1 = l2.Id and l2.Id+1 = l3.Id and l1.Num = l2.Num and l2.Num = l3.Num
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