查找连续模式（使用 SQL）

Question

PostgreSQL 中的表consecutive： 每个se_id 都有一个idx 从 0 到 100 - 这里是 0 到 9。

搜索模式：

SELECT *
FROM consecutive
WHERE val_3_bool = 1
AND val_1_dur > 4100 AND val_1_dur < 5900

现在我正在寻找这种模式的最长连续出现时间 对于每个p_id - 和计数val_1_dur 的AVG。

可以用纯 SQL 计算吗？

table as txt "Result" as txt

Answer 1

一种方法是行号的差异方法来获取每个序列：

select pid, count(*) as in_a_row, sum(val1_dur) as dur
from (select t.*,
             row_number() over (partition by pid order by idx) as seqnum,
             row_number() over (partition by pid, val3_bool order by idx) as seqnum_d
      from consecutive t
     ) t
group by (seqnun - seqnum_d), pid, val3_bool;

如果您专门寻找“1”值，则将where val3_bool = 1 添加到外部查询中。为了理解为什么会这样，我建议你盯着子查询的结果，这样你就可以理解为什么差异定义了连续的值。

然后您可以使用distinct on 获得最大值：

select distinct on (pid) t.*
from (select pid, count(*) as in_a_row, sum(val1_dur) as dur
      from (select t.*,
                   row_number() over (partition by pid order by idx) as seqnum,
                   row_number() over (partition by pid, val3_bool order by idx) as seqnum_d
            from consecutive t
           ) t
      group by (seqnun - seqnum_d), pid, val3_bool;
     ) t
order by pid, in_a_row desc;

distinct on 不需要额外的子查询级别，但我认为这使逻辑更清晰。

Answer 2

有窗口函数，可让您将一行与上一行和下一行进行比较。

https://community.modeanalytics.com/sql/tutorial/sql-window-functions/ https://www.postgresql.org/docs/current/static/tutorial-window.html

如How to compare the current row with next and previous row in PostgreSQL? 和Filtering by window function result in Postgresql 所见