LeetCode180-MySQL-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               |
+-----------------+

通过Id判断是否连续、通过Num判断是否相同=3个表判断

So show you my code:

# Write your MySQL query statement below
SELECT t1.Num as ConsecutiveNums
FROM logs AS t1, logs AS t2, logs AS t3
WHERE t1.Id = t2.Id-1 and t2.Id = t3.Id-1 and t1.Num = t2.Num and t2.Num = t3.Num
GROUP BY t1.Num

Runtime: 348 ms

注意：不能省略GROUP BY t1.Num

一旦省略，则对于连续出现3次以上的数（如：3、3、3、3），查询结果为（3，3），GROUP BY的作用相当于是去重