SQL Window Max（）函数在代码中有问题

Question

我正在编写一个窗口函数，应该创建一个月窗口，并且仅在所述月窗口内的更新标志字段中获取具有最大值的记录。

我的窗口函数有问题，当它仅应显示最大值时，它仍在窗口中显示所有结果。

我在下面留下了我的代码。请帮助。

SELECT 
  gb1.SKU_Id,
  gb1.Warehouse_Code,
  gb1.Period_Start,
  gb1.country,
  tm.c445_month,
  tm.report_date,
  gb1.update_flag,               
  max(gb1.update_flag) over (partition by tm.yearmonth order by gb1.update_flag range between unbounded preceding and current row ) as update_window,
  SUM(gb1.TOTAL_NEW_SALES_FORECAST) AS dc_forecast
FROM BAS_E2E_OUTPUT_GLOBAL_FCST gb1
  inner join (
    SELECT
       gb2.SKU_Id,
       gb2.Warehouse_Code,
       gb2.Period_Start,
       gb2.country,
       gb2.update_flag,
       gb2.report_date,
       tm1.week_date,
       tm1.c445_month,
       tm1.yearmonth
   FROM BAS_E2E_OUTPUT_GLOBAL_FCST as gb2
     left join (
       select distinct(week_date) as week_date,
              c445_month, 
              yearmonth 
       from "PROD"."INV_PROD"."BAS_445_MONTH_ALIGNMENT" 
       group by c445_month, week_date, yearmonth 
     ) as tm1 on gb2.report_date = tm1.week_date
   group by SKU_Id,
            Warehouse_Code,
            Period_Start,
            country,
            update_flag,
            report_date,
            tm1.week_date,
            tm1.c445_month,
            tm1.yearmonth
  ) as tm 
     on gb1.report_date = tm.week_date
    and  gb1.SKU_ID = tm.sku_id
    and gb1.Warehouse_Code = tm.warehouse_code
    and gb1.Period_Start  = tm.period_start
    and gb1.country = tm.country
GROUP BY
    gb1.SKU_Id,
    gb1.Warehouse_Code,
    gb1.Period_Start,
    gb1.country,
    tm.c445_month,
    tm.yearmonth,
    tm.report_date,
    gb1.update_flag

Answer 1

您当前正在使用MAX，并且该窗口被定义为上一行，包括当前行。因此，正确地，它返回的最大值可能应该为每个记录更改。也许您想将max超过固定分区：

MAX(gb1.update_flag) OVER (PARTITION BY tm.yearmonth) AS update_window

顺便说一句，如果您did确实打算将MAX与当前的窗口逻辑一起使用，则在大多数SQL版本中，ORDER BY子句可以简化为：

MAX(gb1.update_flag) OVER (PARTITION BY tm.yearmonth ORDER BY gb1.update_flag) AS update_window

即，默认范围在当前行之前是无界的，因此不必这么说。