如何显示 "each" 个月的最新记录，仅给出每条记录的日期范围

Question

我有一个历史记录 table，其中包含每个客户的记录，其中 start_date 和 end_date 列指示每行的有效期。 table 看起来像这样：

| ID  | Name | Code  |start_date (Timestamp) |end_date (Timestamp) |
|:--- |:----:|:-----:|----------------------:|--------------------:|
|123  | John | 100   |2021/1/6   8:00:00     |2021/1/31  8:00:00   | 
|123  | John | 101   |2021/1/31  8:00:00     |2021/2/15  8:00:00   | 
|123  | John | 102   |2021/2/15  8:00:00     |2021/3/15  8:00:00   | 
|123  | John | 103   |2021/3/15  8:00:00     |2021/6/15  9:00:00   | 
|123  | John | 105   |2021/6/15  9:00:00     |2021/6/15  9:15:00   | 
|123  | John | 106   |2021/6/15  9:15:00     |2021/6/15 10:00:00   |
|123  | John | 107   |2021/6/15 10:00:00     |2021/7/15 15:00:00   | 
|123  | John | 108   |2021/7/15 15:00:00     |null                 |

我决定使用“扩展”功能来生成一个显示“每月”记录（每个月末记录）的列。所需的输出应如下所示，如果 end_date 为空，则应将记录扩展到当前日期，但我的扩展语法无法正常工作：

| ID  | Name | Code  |start_date (Timestamp) |end_date (Timestamp) |end_of_month
|---- |------|-------|-----------------------|---------------------|------------
|123  | John | 101   |2021/1/31  8:00        |2021/2/15  8:00:00   | 2021/1/31
|123  | John | 102   |2021/2/15  8:00        |2021/3/15  8:00:00   | 2021/2/28
|123  | John | 103   |2021/3/15  8:00        |2021/6/15  9:00:00   | 2021/3/31
|123  | John | 103   |2021/3/15  8:00        |2021/6/15  9:00:00   | 2021/4/30
|123  | John | 103   |2021/3/15  8:00        |2021/6/15  9:00:00   | 2021/5/31
|123  | John | 107   |2021/6/15 10:00        |2021/7/15 15:00:00   | 2021/6/30
|123  | John | 108   |2021/7/15 15:00        |?                    | 2021/7/30
|123  | John | 108   |2021/7/15 15:00        |?                    | 2021/8/31
|123  | John | 108   |2021/7/15 15:00        |?                    | 2021/9/30

我有以下 sql 但它不包括最后一条记录，即 end_of 月“2021/9/30”。如果我将 ANCHOR 设置为“MONTH_BEGIN”，则会出现记录“2021/9/30”，但它会排除 return.

中的记录 2021/7/30

select a.id, a.name, a.code, a.start_date, a.end_date, last_day(BEGIN(bg2)) 
as end_of_month from (select id, name, code, start_date, end_date, 
period(start_date,COALESCE(MIN(start_date) OVER (PARTITION BY name ORDER BY start_date 
ROWS BETWEEN 1 FOLLOWING AND 1 FOLLOWING), CURRENT_TIMESTAMP)) as bg from CHESS.HST) as a
expand on bg as bg2 by ANCHOR MONTH_END

Answer 1

这似乎符合您要求的结果：

select a.id, a.name, a.code, a.start_date, a.end_date,
   last_day(begin(bg2)) as end_of_month
from
 (
   select id, name, code, start_date, end_date, 
      period(start_date,COALESCE(end_date
                                ,add_months(CURRENT_TIMESTAMP(0), 1)
                                )
            ) as bg
   from HST
 ) as a
expand on bg as bg2 
    by ANCHOR MONTH_END

如何显示 "each" 个月的最新记录，仅给出每条记录的日期范围

How to show the latest record for "each" month given only a date range of each records

sql

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teradata

history-tables

teradatasql