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Calculate visits based on cutoff date

Calculate visits based on cutoff date

I have a group of patients participating in a special program. I need to compute the number of hospital visits for each patient before and after they joined this program.

Patient table looks like this:


PatientID      ActiveDate           InactiveDate          PreActiveVisits
111              7/1/2016           12/31/2016                   ?

Visits table looks like this:

PatientID           AdmitDate
111                 1/1/2016
111                 2/1/2016
111                 3/1/2016
111                 8/1/2016 

Need to populate the Patient table with a PreActiveVisits total of 3 but I'm not sure how to approach this without using a cursor.

RE: Calculate visits based on cutoff date

Would this query return the correct data?


Select  Visits.PatientId,
        Count(Visits.AdmitDate) As PreActiveVisits
From    Patient
        Inner Join Visits
          On Patient.PatientId = Visits.PatientId
          And Patient.ActiveDate <= Visits.AdmitDate
Group By Visits.PatientId 

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RE: Calculate visits based on cutoff date

Try something like this:


WITH VisitCount (PatientID, VCount) AS
  (SELECT Visits.PatientID, COUNT(AdmitDate) 
     FROM Visits 
       JOIN Patient
         ON Visits.PatientID = Patient.PatientID
     WHERE Visits.AdmitDate < Patient.ActiveDate))

UPDATE Patient
  SET PreActiveVisits = VisitCount.VCount
  WHERE Patient.PatientID = VisitCount.PatientID 


RE: Calculate visits based on cutoff date

That did it - as always you make it look easy. For the update it would be easiest to use this as a cte? Thanks.

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