Gorm Support UNION and UNION ALL

Describe the feature

I am using gorm for mysql and I need to generate UNION and UNION ALL queries.

Motivation

Query optimization and new query support.

Related Issues

N/A

Comment From: github-actions[bot]

This issue has been automatically marked as stale because it has been open 360 days with no activity. Remove stale label or comment or this will be closed in 180 days

Comment From: afbagwell

We had to do workaround using a significant chunk of raw SQL because of the lack of support for UNION keyword. We are using sqlite.