Building a FHIR-Compliant ADT Database: Encounters, Polymorphism, and Facades

If you are a software engineer building a healthcare application today, you're inevitably going to cross paths with HL7 FHIR (Fast Healthcare Interoperability Resources). FHIR is fantastic as a standardized API format for exchanging healthcare data. But when it comes time to actually store that data in a traditional relational database (SQL), things get complicated fast.

Today, we're going to look at how to design a database architecture for a core hospital workflow: ADT (Admission, Discharge, Transfer) . We'll explore why standard SQL design patterns don't always apply, the headache of polymorphic relationships, and how real-world systems handle these challenges.

1. The End of Fragmented Visit Tables

In a legacy hospital system, you might expect to see a database schema that looks like this:

table_outpatient_visits

table_inpatient_admissions

table_er_logs

FHIR completely rejects this pattern.…