Yes, you will need to use group by over all fields with no aggregation, or separate the load statement.
Imagine the following:
Year Unit Sales 2008 A 5000 2008 B 8000 2009 A 6000 2009 B 5000
Now if you want to sum up the Sales and group it by Year you will end up with:
Year Sum(Sales) 2008 13000 2009 11000
This looks ok and is what we would expect. If we also added the Unit and did not group by the Unit value, what would we expect to see?
Year Unit Sum(Sales) 2008 A 13000 2008 B 13000 2009 A 11000 2009 B 11000
This is obviously wrong so you have to group by the fields that are not part of an aggregation. Or just load Date_Short and your aggregation in one table and you can either join that to the table one way or another or keep it separated and linked with Date_Short as the key field.