【Leetcode】Consecutive Numbers

题目链接：https://leetcode.com/problems/consecutive-numbers/

题目：

Write a SQL query to find all numbers that appear at least three times consecutively.
+—-+—–+ 
 | Id | Num | 
 +—-+—–+ 
 | 1 | 1 | 
 | 2 | 1 | 
 | 3 | 1 | 
 | 4 | 2 | 
 | 5 | 1 | 
 | 6 | 2 | 
 | 7 | 2 | 
 +—-+—–+ 
 For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.

思路：
三表联查，注意多表联合join的用法

算法：

select distinct l1.num from (Logs l1 inner join Logs l2 on l1.num=l2.num and l1.id+1=l2.id) inner join Logs l3 on l1.num=l3.num and l1.id+2=l3.id