案例表达式返回两个条件的值

Question

当AAALTLCHANGEVALUE等于“ Manual Rate”时，我需要返回初始AAALTLCHANGEREASON值。因此，在此示例中，我需要返回“需要的类”。

AAALTLCHANGEVALUE   AAALTLCHANGEREASON         CREATEDDATETIME     
ManualCoded              New Customer           09/17/2019          
Manual Rate              Class needed           09/18/2019
CWI Inspection           Reweigh                09/19/2019
Manual Rate              Insurance Added        09/20/2019

我尝试过这种情况下的表达式，但没有成功：

case

when  [AAALTLCHANGEVALUE] = 'manual rate' then[AAALTLCHANGEREASON]
when  [AAALTLCHANGEVALUE] = 'manual rate' then MIN[CREATEDDATETIME]

else null

end

感谢您的帮助。

Answer 1

首先选择所有'Manual Rate'，然后确保没有其他人早于该行。

SQL DEMO

 SELECT AAALTLCHANGEREASON
 FROM YourTable t1
 WHERE AAALTLCHANGEVALUE = 'Manual Rate'
   AND NOT EXISTS (SELECT 1
                   FROM YourTable t2
                   WHERE t2.CREATEDDATETIME < t1.CREATEDDATETIME
                     AND AAALTLCHANGEVALUE = 'Manual Rate')

Answer 2

您可以使用top和order by：

select TOP AAALTLCHANGEREASON
from t
where AAALTLCHANGEVALUE = 'manual rate'
order by CREATEDDATETIME;