I need a little help as I am a complete novice at scripting in unix. However, i am posed with an issue... i have two csv files in the following format@

FILE1.CSV:
HEADER
HEADER
Header
, , HEADER
001X ,,200
002X ,,300
003X ,,300
004X ,,300


FILE2.CSV:
HEADER
HEADER
Header
, , HEADER
001X ,,300
003X ,,500
005X ,,600
006X ,,100


I need the above to files to merged into on final file as below:

FINAL_MERGED.CSV:
HEADER
HEADER
Header
, , HEADER
001X ,,300
002X ,,300
003X ,,500
004X ,,300
005X ,,600
006X ,,100


I have tried using the join command but that only lets me to join the two files but as you can see from the above i need the ability to be able to overwrite values from file 1 whith those in file 2.

The logic behind it is that the first csv (FILE1.CSV) file is produced but may have incorrect figures associated with it. Once the information is readily available the second csv (FILE2.CSV) is produced with the correct figures and any missing codes.

Once this has been done file 1 and file 2 need to be merged to have the correct figures from file 2 and also to include any missing codes that are on file 2 but not file 1.

I need to do this in Unix, my initial thoughts were to use the join command but not sure if this is possible but may be some use of lookup could be done... again i am a programming and unix newbie so would appreciate any assistance.