PostgreSQL按间隔分组 [英] PostgreSQL group by with interval

问题描述

嗯，我有一组看似简单的数据，但这给我带来了很多麻烦。

Well, I have a seemingly simple set of data but it gives me a lot of trouble.

这是我的数据看起来像的一个例子：

This is an example of what my data look like:

quantity  price1  price2 date
100       1       0      2018-01-01 10:00:00
200       1       0      2018-01-02 10:00:00
50        5       0      2018-01-02 11:00:00
100       1       1      2018-01-03 10:00:00
100       1       1      2018-01-03 11:00:00
300       1       0      2018-01-03 12:00:00

我需要对按 price1和 price2分组的数量列进行汇总，这很容易，但是我需要考虑 price1和 price2的时间变化。数据按日期排序。

I need to sum up "quantity" column grouped by "price1" and "price2" and it would be very easy but I need to take into account time changes of "price1" and "price2". Data is sorted by "date".

我需要的是最后一行不与前两个分组，尽管它的 price1和 price2具有相同的值。我还需要获取每个间隔的最小和最大日期。

What I need is the last row to be not grouped with the first two although it has the same values for "price1" and "price2". Also I need to get minimal and maximal date of each interval.

最终结果应如下所示：

quantity price1 price2 dateStart            dateEnd
300      1      0      2018-01-01 10:00:00  2018-01-02 10:00:00 
50       5      0      2018-01-02 11:00:00  2018-01-02 11:00:00
200      1      1      2018-01-03 10:00:00  2018-01-03 11:00:00
300      1      0      2018-01-03 12:00:00  2018-01-03 12:00:00

对SQL查询有任何建议吗？

Any suggestions for a SQL query?

推荐答案

这是一个空白和孤岛的问题。使用以下代码：

It is a gap and island problem. Use the following code:

select sum(quantity), price1, price2, min(date) dateStart, max(date) dateend 
from
(
    select *,
           row_number() over (order by date) -
           row_number() over (partition by price1, price2 order by date) grp
    from data
) t
group by price1, price2, grp
order by dateStart

dbfiddle演示

该解决方案基于对 price1 和 price2 的连续序列的识别，这是通过创建 grp 列来完成的。一旦分离出连续的序列，就可以使用 grp 进行简单分组。

The solution is based on an identification of consecutive sequences of price1 and price2, which is done by a creation of the grp column. Once you isolate the consecutive sequences then you do a simple group by using grp as well.

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