LeetCode数据库题目

题目

编写一个 SQL 查询，查找所有至少连续出现三次的数字。

+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+

例如，给定上面的 Logs 表， 1 是唯一连续出现至少三次的数字。

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

思路

1. 查询目标：Num (As ConsecutiveNums)
2. 查询范围：Logs表
3. 查询条件：所有至少连续出现三次的数字

解答

select distinct
    l1.Num as ConsecutiveNums
from
    Logs as l1,Logs as l2,Logs as l3
where
    l1.Num = l2.Num and l2.Num = l3.Num and l1.Id = l2.Id -1 and l2.Id = l3.Id -1