Leetcode: 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.

Required:
appear 3 times consecutively.

Code 1: For every row, check its next row and then the next.

select a.Num from Logs a where exists ( select 1 from Logs b where a.Id+2 = b.Id and a.Num = b.Num ) and exists ( select 1 from Logs b where a.Id+1 = b.Id and a.Num = b.Num )

O(n^3) time complexity.

Code 2:

select distinct a.Num
from Logs a, Logs b, Logs c
where
a.Id = b.Id+1 and a.Id = c.Id+2 and a.Num = b.Num and a.Num = c.Num

SQL is just programming language. First you need to be quite familar with the API that you can use. Then you have to think method or algorithem to solve problems.