如何获取先前的行值 Teradata答案

【问题标题】：How to get previous row values Teradata如何获取先前的行值 Teradata
【发布时间】：2021-09-18 13:29:24
【问题描述】：

我有以下格式的数据

 Id    Code    Date         Amount       Type
 101   B25     5/4/2020      $500         C
 101   A15     5/5/2020      $100         D
 101   D15     5/5/2020      $200         D
 102   B35     6/2/2020      $400         C
 102   A15     6/2/2020      $50          D

我需要以下内容

 Id    Code    Date         Amount       Type  C_Date          C_Amount
 101   A15     5/5/2020      $100         D    5/4/2020         $500
 102   A15     6/2/2020      $50          D    6/2/2020         $400

对于所有 Code='A15' 我需要上一行的日期和金额，其中 Type='C'

我做了这个

 Select id, Amount, Date,
  sum(Amount) over (partition by ID ROWS between UNBOUNDED PRECEDING and CURRENT ROW) as 
   C_Amount,
  Max(Date) over (partition by ID ROWS between UNBOUNDED PRECEDING and CURRENT ROW) as 
   C_Date
 from Table
 where code='A15' or Type='C'

输出不是我们想要的

 Id    Code    Date         Amount       Type  C_Date          C_Amount
 101   A15     5/5/2020      $100         D    ***5/5/2020         $100***
 102   A15     6/2/2020      $50          D    ***6/2/2020         $50***

感谢任何帮助

【问题讨论】：

标签： row teradata lag

【解决方案1】：

答案集与您的查询不匹配，它也将包含“C”行。

ROWS between UNBOUNDED PRECEDING and CURRENT ROW 是一个组和。

您需要ROWS between 1 PRECEDING and 1 PRECEDNG 和一个 ORDER BY 来获取上一行的值。

最好切换到 LAG 或 LAST_VALUE，这更简单，并且允许处理“A15”和前一个“C”行之间的额外行：

 Select id, Amount, Date,
  LAG(case when Type='C' then Amount end IGNORE NULLS)
  over (partition by ID
        order by date) as C_Amount,
  LAG(case when Type='C' then date end IGNORE NULLS)
  over (partition by ID
        order by date) as C_Date
 from Table
 where code='A15' or Type='C'
 qualify code='A15';

【讨论】：