Consecutive_Numbers.sql

/*
Consecutive Numbers
https://leetcode.com/problems/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.

+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+
*/

SELECT DISTINCT(l1.Num) AS ConsecutiveNums
FROM
    Logs l1, Logs l2, Logs l3
WHERE (
       l1.Num = l2.Num AND l1.Id = (l2.Id + 1) AND
       l2.Num = l3.Num AND l2.Id = (l3.Id + 1)
)