Syncing Tables

I have source data in a table in an excel sheet.
Amongst other things, I need to store a copy of that data in a table on a sql server database.

How can I sync these?

Here is what I have come up with,

Q1 delete from local table
Q2 append local table from excel data
Q3 delete from sqlserver left join local data where local id is null
Q4 append local data left join sqlserver into sqlserver where
sqlserver's id is null.

I do the Q3/Q4 delete and append, because copying the full table takes aorund 20 minutes, but in reality only about 100 records change from day to day, and Q3/Q4 runs about 2 minutes.

This works, BUT, it is possibly that the excel data could be empty, at which point, I would want to keep the old data on the sqlserver. The sequence above would erase the old data.

So two questions
1) is there a way to sync the excel source with the sqlserver destiantion without using the local copy?

2) Is there a way to preserve the sqlserver data if the excel file is empty?

Thanks,
David