Filtering preserves SQL three-valued negation, and projection preserves duplicate rows unless DISTINCT is explicitly requested

Filtering preserves SQL three-valued negation, and projection preserves duplicate rows unless DISTINCT is explicitly requested. The complete application includes native models, services, repository projections, a working preview and visible acceptance cases. Preserve the other documented invariants and run bash test/run.sh.

Work with the stack you want to practice. Your workspace and timer start after you choose.