180 Consecutive Numbers
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.
SELECT DISTINCT
l1.Num
FROM
LOGS l1,
LOGS l2,
LOGS l3
WHERE l1.Id = l2.Id - 1
AND l2.Id = l3.Id - 1
AND l1.Num = l2.Num
AND l2.Num = l3.Num
三张表自己连接，根据ID的连续性找到连续出现的数字。
找出这些数字以后再使用 DISTINCT 关键字去重一下。
