Consecutive Numbers
Preview mode. Log in to edit, run, submit, and save progress.
Medium
Description
You are given a Logs table that records numbers against sequential IDs. Write a SQL query to find all numbers that appear at least three times consecutively (i.e., in three consecutive rows ordered by id). Return the result in any order with no duplicates.
Database Schema
Logs
| Column Name | Example Value |
|---|---|
| id | 1 |
| num | 1 |
Example
Logs
| id | num |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 1 |
| 6 | 2 |
| 7 | 2 |
Output
| ConsecutiveNums |
|---|
| 1 |
Explanation:
1 appears at ids 1, 2, 3 consecutively. 2 never appears three times in a row.
Approach hint
Start with a simple approach, explain the trade-off, then move toward a cleaner or more scalable solution.
Common mistake
Skipping assumptions, edge cases, or trade-offs can make an otherwise good answer feel incomplete.
SQL Editor
Loading...
Logs
| id | num |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 1 |
| 6 | 2 |
| 7 | 2 |
Output
| ConsecutiveNums |
|---|
| 1 |