Oracle 使用特定值更新最后一个条目列

Question

我正在尝试在 Oracle Apex 平台上更新表中的一行，更具体地说，是从具有相同序列号的最后一个条目中获取 present_indication 值，并将其作为 previous_indication 放在新行中。 我的表 HYDRO_COUNTS 是这样的：

OID,SERIAL_NUMBER,PROV_NUMBER,HDRCNTS_PREVIOUS_IND,HDRCNTS_PRESENT_IND 

到目前为止，我已经尝试了很多关于使用相同的 SERIAL_NUMBER 和 PROV_NUMBER 获取最后输入的值的查询，但没有任何效果。这是我的更新查询。

UPDATE HYDRO_COUNTS
SET HDRCNTS_PREVIOUS_IND = (SELECT HDRCNTS_PRESENT_IND FROM HYDRO_COUNTS WHERE PROV_NUMBER = 
:P20_PROV_NUMBER AND SERIAL_NUMBER = :P20_SERIAL_NUMBER )
WHERE OID = :P20_OID ;

Answer 1

如果OID 是一个始终递增的唯一列，您可以执行类似的操作

UPDATE HYDRO_COUNTS
  SET HDRCNTS_PREVIOUS_IND = (SELECT HDRCNTS_PRESENT_IND
                                FROM HYDRO_COUNTS
                                WHERE PROV_NUMBER = :P20_PROV_NUMBER AND
                                      SERIAL_NUMBER = :P20_SERIAL_NUMBER AND
                                      OID = (SELECT MAX(OID)
                                               FROM HYDRO_COUNTS
                                               WHERE PROV_NUMBER = :P20_PROV_NUMBER AND
                                                     SERIAL_NUMBER = :P20_SERIAL_NUMBER AND
                                                     OID < :P20_OID)
  WHERE OID = :P20_OID