Currently the Query object does not allow to create a UNION of tables, which is quite a shortcoming forcing you to either use multiple query objects or other workarounds involving more coding.

The request for UNION was already raised in this idea https://experience.dynamics.com/ideas/idea/?ideaid=972a4dde-fc90-e911-80e7-0003ff68e84c, but was asking for much more and was rejected and this also the request for UNION.
Category: Development
Needs Votes
Ideas Administrator

Thank you for this suggestion! Currently this is not on our roadmap. We are tracking this idea and if it gathers more votes and comments we will consider it in the future. Best regards, Business Central Team