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The raw csv format tables can be imported as "Text File" (External Data tab).
Demographics
Import this as a table Patients.
Load PATIENT_ID as textShort Text, since Long Integer is too short, and double double has problems (at least 10 selected PATIENT_ID's would not match when used to select using the same ID).
Demographics
Import this as a table Patients.
Encounters:
set PAT_ENC_CSN_ID to double
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