Leetcode No.180 连续出现的数字

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| num         | varchar |
+-------------+---------+
id 是这个表的主键。

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

Result 表：
+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+
1 是唯一连续出现至少三次的数字。

select distinct(Num) ConsecutiveNums
from(
    select Num,
    lag(Num,1)over(order by id desc) as last1,
    lag(Num,2)over(order by id desc) as last2
    from Logs
)a
where Num=last1 and Num=last2