嵌套案例语句 Teradata 将时间戳（0）、时间戳（6）转换为日期并进行比较

Question

  I want to generate qualify_flag as '1' always when device_end_dt = '9999-12-31 23:29:59'. If it is 
 not '9999-12-31 23:29:59' then if DEVICE_END_DT + 1 day = CREATION_DATE then qualify_flag is 0 else 1. 
DEVICE_END_DT is TIMESTAMP(0), CREATION_DATE  is TIMESTAMP(6). 
CREATION_DATE column doesn't have any value which is '9999-12-31'.

以下 case 语句因日期无效而失败，似乎 '9999-12-31' 以某种方式出现，而 ('9999-12-31' + 1) 则模棱两可。

select
case When 
        Cast(DEVICE_END_DT AS DATE) <> CAST('9999-12-31' AS DATE) 
            THEN
                case when CAST((Cast(DEVICE_END_DT AS DATE) + 1) AS DATE) = Cast(CREATION_DATE AS DATE)
                        then 0
                        else 1
                end

case when   
        Cast(DEVICE_END_DT AS DATE) = CAST('9999-12-31' AS DATE) 
            THEN
                            1 
end 
end as qualify_flag
 FROM ABC;

Answer 1

这是您的逻辑简化：

CASE 
  WHEN Cast(DEVICE_END_DT AS DATE) = Cast(CREATION_DATE AS DATE) - 1
  THEN 0
  ELSE 1
END

顺便说一句，最好使用 日期文字 DATE '9999-12-31' 而不是 CAST('9999-12-31' AS DATE)。

您要解决的最后一个业务问题是什么？看起来像是在缓慢变化的维度中识别不良数据。