Cross table queries????

I would like to know if it's possible within ado.net to perform a cross table query.

Within my application, I have performed the following steps

1. Get master data from production database
2. Clone master database table to create a working version
3. Fill working table with current data from another source
4. Merge working table with master (adding new/amending existing)
5. Write master table back to production database

One step I'm having trouble with is how to remove any records in the master table which are no longer present in the working table.

Table structure is very simple

Server_id
Software_name
Software_version

The application adds/amends any data from a number of reporting servers, not all servers will report. Therefore I do not wish to simply replace the master table with the working one. I only need to remove software_name & version information if a reporting server no longer provides the information.

Currently I'm using a series of FOR loops to scan through the data and remove any obsolete records, but this is painfully slow.

Is there a better way to do this task?

Thanks for any pointers.

I don't understand what you are trying to do. Can you explain a bit more clearly?