Question

我想在BigQuery中合并相邻的日期范围。

我有一张这样的桌子：

ID   START                     END
1    2019-01-18 17:34:58 UTC   2019-02-18 12:14:59 UTC
1    2019-02-18 06:04:39 UTC   2019-02-18 08:05:05 UTC
1    2019-02-18 08:05:05 UTC   2019-02-18 10:06:05 UTC
1    2019-02-18 10:06:05 UTC   2019-02-19 11:16:15 UTC
2    2019-01-19 06:02:29 UTC   2019-01-29 11:02:23 UTC

由于中间三行表示一个分为三部分的单个范围，因此我想将它们组合起来，因此表格如下所示：

ID   START                     END
1    2019-01-18 17:34:58 UTC   2019-02-18 12:14:59 UTC
1    2019-02-18 06:04:39 UTC   2019-02-19 11:16:15 UTC
2    2019-01-19 06:02:29 UTC   2019-01-29 11:02:23 UTC

完成此任务的最佳方法是什么？

Answer 1

您需要确定范围的起始位置。就您而言，它们似乎具有完全匹配的结束和开始位置，因此您可以使用lag()来确定组从何处开始。起始次数的累积计数提供了一个分组ID，可用于聚合：

select id, min(start) as start, max(end) as end
from (select t.*, countif(prev_end is null or prev_end <> start) over (partition by id order by start) as grp
      from (select t.*, lag(end) over (partition by id order by start) as prev_end
            from t
           ) t
     ) t
group by id, grp;

如果组可以重叠，则通常可以通过累积最大值来达到目的：

select id, min(start) as start, max(end) as end
from (select t.*, countif(prev_end is null or prev_end <> start) over (partition by id order by start) as grp
      from (select t.*,
                   max(end) over (partition by id order by start rows between unbounded preceding and 1 preceding) as prev_end
            from t
           ) t
     ) t
group by id, grp;

SQL / BigQuery中的组合范围

1 个答案: