Question

PostgreSQL中的表import os from os import system for ele in os.listdir(Path): if ele.endswith('.sdf'): chdir(Path + '/' + ele[0:5]) system('cat' + ' ' + '*.sdf' + '>' + ele[0:5] + '.sdf')：每个consecutive都有一个se_id 从0到100 - 这里是0到9。

搜索模式：

idx

现在我正在寻找这种模式连续出现的最长时间对于每个SELECT * FROM consecutive WHERE val_3_bool = 1 AND val_1_dur > 4100 AND val_1_dur < 5900 - 以及p_id的{{1}}。

是否可以在纯SQL中计算？

table as txt "Result" as txt

Answer 1

一种方法是使用行数方法的差异来获取每个的序列：

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;

如果您正在寻找＆＃34; 1＆＃34;值，然后将where val3_bool = 1添加到外部查询。为了理解为什么会这样，我建议你盯着子查询的结果，这样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

获取最大值

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不需要额外级别的子查询，但我认为这会使逻辑更清晰。

Answer 2

有一些窗口函数，可以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

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

查找连续模式（使用SQL）

2 个答案: