I am querying data from a database into a table in Perspective. I have changed the session locale to Danish (da-DK) and also changed the regional settings in Windows to use European number formatting. However, the numbers in my table are still displayed using the American format (e.g., 1,000,000.00 instead of 1.000.000,00). How can I display the numbers using European formatting?
This looks like a long standing bug. Try the workaround in this post which seems to refresh the number format for the entire page:
Just a clarification: the problem isn't database related. It's just a problem of rendering the data on the table - no matter where it comes from.
(The question title sounds like you want the query to return the number as a string. This is generally a bad idea, so trying to fix the rendering is a good one!)

