How to update linked box in Visio when the source disappears

I have a Visio diagram where some boxes are linked to access database queries. These queries count certain values by category, for example:

High: 2

Medium: 3

Low: 1

and so on, however, if any of the categories does not have value anymore, the query does not return it but that does not reflect in Visio. I would like to still see the category in visio but the value would be Zero, is that possible?