SQL--leetcode180. 連續出現的數字

編寫一個 SQL 查詢，查找所有至少連續出現三次的數字。

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

例如，給定上面的 Logs 表， 1 是唯一連續出現至少三次的數字。

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

---

這一題主要考察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