I am writing an SSIS package to run on SQL Server 2008. How do you do an UPSERT in SSIS?
IF KEY NOT EXISTS INSERT ELSE IF DATA CHANGED UPDATE ENDIF ENDI
Apart from T-SQL based solutions (and this is not even tagged as sql/tsql), you can use an SSIS Data Flow Task with a Merge Join as described here (and elsewhere).
The crucial part is the Full Outer Join in the Merger Join (if you only want to insert/update and not delete a Left Outer Join works as well) of your sorted sources.
followed by a Conditional Split to know what to do next: Insert into the destination (which is also my source here), update it (via SQL Command), or delete from it (again via SQL Command).