Implement UNION ALL BY NAME #14508

Is your feature request related to a problem or challenge?

Users may need to combine tables with differing column orders or missing columns as evolving schemas. Currently, AFAIK we require columns to match by position, forcing manual schema adjustments.

Describe the solution you'd like

Implement a UNION ALL BY NAME operator or modify the existing one such that it:

• matches columns by name rather than by position.
• fills missing columns with NULLs.
• optionally supports similar flexibility in INSERT operations (e.g., INSERT INTO ... BY NAME).

Describe alternatives you've considered

No response

Additional context

No response