Question

我有一个像这样的SQLite表：

sqlite> select * from things order by id;
id          created         
----------  ----------------
1           2458171.46967479
2           2458171.46967747
3           2458171.46968049
4           2458171.46968362
5           2458171.46968647
6           2458171.46968948
7           2458171.46969561
8           2458171.46973709
9           2458171.46974006
10          2458171.46974368
11          2458171.46978387

created是一个julianday时间戳。我想选择最近同时记录的最新行组。＆＃34;大约在同一时间＆＃34;在＃100;彼此相差100毫秒之内。＆＃34;

我知道如何将整个表分成谨慎的桶，但我想要的不同之处。例如（并且这与上面的表格不匹配），让我们说最近的记录的时间戳为0.下一个最近的记录的时间戳为+75，最近的第三个记录的时间戳为时间戳为+160。

或换句话说：

id     tstamp
------ -------
156    0
155    75
154    160

如果我的阈值为50，则只返回＃156。
如果我的阈值是75，那么应该返回＃156和＃155。
如果我的阈值是85，则应返回所有三个，因为160在下一个最近一行的85之内。

有关如何进行的任何建议？我可以在应用程序代码中完成它，但如果可以的话，它在SQL中要快得多。我怀疑我可能需要用WITH RECURISIVE做一些事情吗？

Answer 1

阅读WITH RECURSIVE文档之后：https://www.sqlite.org/lang_with.html

这是我的解决方案：

WITH RECURSIVE
    what(x) AS (
        SELECT max(created) FROM things
        UNION
        SELECT things.created FROM what, things
        WHERE things.created >= (what.x - 85)
    )
SELECT x FROM what ORDER BY 1;

这里有一些示例查询显示它有效：

sqlite> select * from things;
id          created   
----------  ----------
1           160       
2           85        
3           0         

sqlite> WITH RECURSIVE
   ...>     what(x) AS (
   ...>         SELECT max(created) FROM things
   ...>         UNION
   ...>         SELECT things.created FROM what, things
   ...>         WHERE things.created >= (what.x - 50)
   ...>     )
   ...> SELECT x FROM what ORDER BY 1;
x         
----------
160       

sqlite> WITH RECURSIVE
   ...>     what(x) AS (
   ...>         SELECT max(created) FROM things
   ...>         UNION
   ...>         SELECT things.created FROM what, things
   ...>         WHERE things.created >= (what.x - 75)
   ...>     )
   ...> SELECT x FROM what ORDER BY 1;
x         
----------
85        
160       

sqlite> WITH RECURSIVE
   ...>     what(x) AS (
   ...>         SELECT max(created) FROM things
   ...>         UNION
   ...>         SELECT things.created FROM what, things
   ...>         WHERE things.created >= (what.x - 85)
   ...>     )
   ...> SELECT x FROM what ORDER BY 1;
x         
----------
0         
85        
160

近期SQLite分组

1 个答案: