数据表信息:

logs 表, 包含对应的编号 id, 和出现的数字Num.

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

话不多说, 再看需求~

需求:

编写一个 SQL 查询，查找所有至少连续出现三次的数字。输出如下结果:

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

话不多说, 进行拆解~

拆解:

这里首先想到的是使用lead窗口函数, 将当前结果往后移动一个, 往后移动二个, 当三者结果一致, 则说明该数字出现过三次.

直接上SQL语句:

sql 复制代码

select 
id, num,
lead(num, 1) over(order by id) as num_1,
lead(num, 2) over(order by id) as num_2
from logs 
;

结果如下:

再加上限制条件:

sql 复制代码

select t.id   
from (
    select 
    id, num,
    lead(num, 1) over(order by id) as num_1,
    lead(num, 2) over(order by id) as num_2
    from logs 
) as t 
where t.num = t.num_1
and t.num = t.num_2
;

就可以得到最终的结果:

最后给大家介绍一下我这边的操作步骤, 想要自己测试的话, 可以参考:

sql 复制代码

CREATE TABLE logs (
    Id INT,
    Num INT
);

INSERT INTO logs (Id, Num)
VALUES (1, 1), (2, 1), (3, 1), (4, 2), (5, 1), (6, 2), (7, 2);