Simple update problem

Hello. I have a table that stores readings from temperature sensors every 15 minutes. My problem is that one of them had a problem and kept reading the same temperature for a couple of days. Luckily (and surprisingly), this particular one is one of the few that had a backup sensor. So, what I am trying to do is update the problem sensor's readings with the backup sensor's readings for an approximately two day period. I am having trouble with the syntax on the update. Can anyone help?

Here is the table info:

SQL> describe temperature_log

 Name                                      Null?    Type
 ----------------------------------------- --------
----------------------------
 SYSTEM_TIMESTAMP                          NOT NULL DATE
 SENSOR_ADDRESS                            NOT NULL VARCHAR2(4)
 DEGREES_F                                 NOT NULL NUMBER(38)
 DEGREES_C                                 NOT NULL VARCHAR2(8)

I am trying to put the two temp fields from the rows with an 'FFFF' address into the rows with a '6DA9' address for a period of time.

Thanks.
Bill Received on Sat May 21 2005 - 17:18:14 CDT