按最新值分组 sql

Question

Forecast date            date          Value  Object     Demand or supply
01-01-2016 00:30    12-10-2019 00:00    85    Ice-cream     Demand
04-07-2018 02:59    26-12-2019 00:00    83    Crisps        Supply
07-08-2018 03:25    29-02-2020 00:00    50    Juice         Demand
29-10-2018 03:25    09-05-2020 00:00    76    Juice         Supply
25-02-2019 03:25    07-08-2020 00:00    74    Juice         Demand
01-07-2019 03:25    11-10-2020 00:00    69    Crisps        Demand
17-10-2019 03:25    17-12-2020 00:00    77    Meal          Supply
06-01-2020 03:25    29-03-2021 00:00    87    Eggs          Demand

我有一个 dataframe 像上面一样，随着更多数据可用，预测会在特定日期不断出现

我想获得每个 object 和单独分组需求和供应的特定日期的最新预测值。

Logic-
-Latest forecast date for each date value and object
- Group demand/supply and object with Date desc

所需 output

Forecast Date   Date    Demand or supply    Object  Value
01-01-2020  01-11-2021  Demand            Ice-Cream 60
01-01-2020  01-10-2021  Demand            Ice-Cream 80
01-01-2020  01-09-2021  Demand             Crisps   70
01-01-2020  01-08-2020  Supply             Crisps   70
01-11-2019  01-07-2020  Supply             Crisps   85
01-11-2019  01-06-2020  Supply             Crisps   80

因此，为了清楚地说明日期列中的条目 - 我希望该值是最新预测日期中的值。 - 然后按需求/供应对表格进行分组，然后按 object 分组，最后按日期分组，因此在需求/供应侧为每个 object 获得相应的时间序列值

Answer 1

如果我理解正确，您可以使用row_number() ：

select t.*
from (select t.*,
             row_number() over (partition by object, demand_group, date order by forecast_date desc) as seqnum
      from t
     ) t
where seqnum = 1;