Enhance SQLExecute test coverage

[rolandwalker]

Description

These are regression tests, enforcing current behavior.

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .

[github-actions]

Codex Review

No findings in the PR changes.

Residual risk/testing gap:

• I couldn’t run the test suite in this environment because both uv and pytest are unavailable (command not found), so this review is static-only.