This gets to the forefront of why user stories are so great.
What benefit does upgrading your database give to the end user? None? Then don't spend the time and money doing it. Spend that time and money providing something that will give value to your end user.
If it does? Then think about it the other way. Maybe you can only implement a new feature when you have version x of your database software? In the dependency of the story, you could mention that database upgrade required to provide this feature.
tl;dr Don't just upgrade for the sake of it. Make sure upgrading adds tangible value to your customers.