beginnerWhy ORM Exists — Persistence Fundamentals & the Impedance Mismatch
What is the object-relational impedance mismatch, and can you name three of its five specific faces?
It's the structural mismatch between how Java thinks (objects — nested, referenced, identity-aware) and how a relational database thinks (flat tables, foreign keys only). Three of the five faces: granularity (nested objects vs. flat rows), identity (== reference equality vs. matching primary key values), and associations (direct object references vs. foreign key columns with no built-in navigation).
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