>It's legal to use UNIONs in a view, as long as it's defined with CREATE SQL VIEW and you don't later attempt to modify it with the VFP View Designer.
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>However...
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>Is it good practice to use UNION clause(s) in a view? Or, is that usually a sign that the database should be refactored?

I think using UNION may be a (good) sign that the database is successuflly normalized. Usually views are used to denormalize data for particular uses, such as querying or reporting.