Using ...Schema First..., I have a database structure, as so...ExternalDataItems
---
edataitem_id PK -- surrogate auto-increment - NOT for FK relation here
datahash UX -- Candidate Key / Unique Index (binary(20))
ExternalMaps
---
emap_id P...
2019 Update / TLDR; switch to Entity Framework ...Core... (or whatever else)...While missing some "Features", EF Core properly honors Alternate Keys (aka Unique Constraints) in addition to Primary Keys and thus does a ...much... better job of honoring Rel...