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Clinical data ER-diagrams

(Micheal ) #1

Hello OHDSI!

In this picture,

I want to know about these cardinalities. what are these about?
1:1? 1:N? N:M?

(Anna Karenina) #2

Hello @MichealJeong,

They’re all 1:N, and this is shown on your ER diagram as well.
In other words,

  • Each Care Site should have only one Location. It’s natural that some Care Sites share the same Location (e.g. are in the same city).
  • Each Person should have only one Location. Even if a patient has multiple locations in source data, ETL should choose only one (the most recent is a safe bet).
  • Each Person should have only one associated Provider – primary care provider. See convention #13 in wiki for details.

(Micheal ) #3

Then, when liking care site with location, Is that 1:1 relation?

(Anna Karenina) #4

Nope, it’s 1:N. It can be 1:1 in some cases – when you have the precise address of a Care Site, which makes a Location entry, and no other Care Sites are located at this address. However, even if source data are granular to the most possible extent, I can easily imagine N care sites located in the same building, so the relationship is still 1:N.
In the majority of cases I’ve seen, there’s only a MSA/city level of precision in source data, rarely a ZIP code. Therefore, a single Location is created and many Care Sites are linked to it.