Where ur doing the data feed,first
create a temp table with a flag column

1.insert into a temp table.
2.check if there are any records already present in the main table.
3.if yes then
4.update flag column of the temp table to say 'D' ,for all the matching records found in the main table
5.then delete all the records from the temp table with flag column having value 'D'.
6.and then insert the remaning records from the temp table into the main table.
6.If there are no matching records then update the flag column as 'N'.Then insert all the records from temp table to main table with flag column having value 'N'.

Hope this helps u.

regards
anandkl