Problem
Table: Logs
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| id | int |
| num | varchar |
+-------------+---------+
id is the primary key for this table.
id is an autoincrement column.
Write an SQL query to find all numbers that appear at least three times consecutively.
Return the result table in any order.
The query result format is in the following example.
Examples
Example 1:
Input: Logs table:
+----+-----+
| id | num |
+----+-----+
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 1 |
| 6 | 2 |
| 7 | 2 |
+----+-----+
Output:
+-----------------+
| ConsecutiveNums |
+-----------------+
| 1 |
+-----------------+
Explanation: 1 is the only number that appears consecutively for at least three times.
Solution
Method 1 - Self join with distinct
SELECT DISTINCT l1.num AS ConsecutiveNums
FROM Logs l1
JOIN Logs l2 ON l1.id = l2.id - 1 AND l1.num = l2.num
JOIN Logs l3 ON l2.id = l3.id - 1 AND l2.num = l3.num;