Two Tables Merge Update

[devbird]

Hello,
I am evaluationg the software and I like to know the following:
Can I merge update two csv files. One is the master file and the other file is the update file.
The Update file is under constand update by its user. Now I need to copy all edited records
from the update file to the master file overwriting the existing old record on the master file.
Also if newly added records to the update files should be copied over and merged with the Master file.

Thanks

[Aaron]

Is the initial update file a complete copy of the master file or a subset of the master file? Also, do the update and master files both have unique keys?