I'd like to extract data from excel file to OLE DB by using SSIS. The source files are some excel files. The identification for each entry is the date.There are some duplicated data between these files.
For example
In file1, the date of entries are from 01/01/13 to 01/15/13.
In file2, the date of entries are from 01/01/13 to 01/31/13. file2 has all the entries which file1 has.
If I run the SSIS package with file1, then all entries in file1 will be imported to OLE DB. If I run the package with file2, then only the different parts in file2 will be imported to OLE DB, the parts which file1 has will not be imported to OLE DB so that it avoids the duplication. If I run file2 one more time, then nothing happens, because all data is in the OLE DB and the new imported data is the duplicated one.
What function should I use in SSIS to do this?