SQL--leetcode180. 连续出现的数字

编写一个 SQL 查询，查找所有至少连续出现三次的数字。

+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+

例如，给定上面的 Logs 表， 1 是唯一连续出现至少三次的数字。

+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+

---

这一题主要考察left join：

# Write your MySQL query statement below
select distinct l1.Num as ConsecutiveNums from Logs l1 
left join Logs l2 on l2.Id=l1.Id+1
left join Logs l3 on l3.Id=l1.Id+2
where l1.Num=l2.Num and l2.Num=l3.Num