180_Consecutive Numbers

[medium]

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 aboveLogstable,1is the only number that appears consecutively for at least three times.

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

Solution 1: Use INNER JOIN

• beat 87%

SELECT DISTINCT l1.Num AS ConsecutiveNums
FROM Logs AS l1
    JOIN Logs AS l2 ON l2.Id - l1.Id = 1 AND l1.Num = l2.Num
    JOIN Logs AS l3 ON l3.Id - l2.Id = 1 AND l2.Num = l3.Num

Solution 2: Use Subquery

• beat 6%

SELECT DISTINCT l1.Num AS ConsecutiveNums
FROM Logs AS l1
WHERE l1.Num = (SELECT Num
            FROM Logs AS l2
            WHERE l2.Id -l1.Id = 1
            )
AND l1.Num = (SELECT Num
            FROM Logs AS l3
            WHERE l3.Id -l1.Id = 2
            );