Question

Patient  ------- PatientID  Visit ----- VisitID PatientID HeartRate VisitDate 

How do I select all of the patients who have a visit, the date of their first visit, and their heart rate at that first visit?

Answer 1

SELECT   p.PatientID,   v.VisitID,   v.HeartRate,   v.VisitDate FROM   Patient p   INNER JOIN Visit v ON p.PatientID = v.PatientID WHERE   v.VisitDate = (     SELECT MIN(VisitDate)      FROM Visit      WHERE PatientId = p.PatientId   ) 

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EDIT: Alternative version. Same thing. (less obvious, therefore less desirable IMHO)

SELECT   p.PatientID,   v.VisitID,   v.HeartRate,   v.VisitDate FROM   Patient p   INNER JOIN Visit v ON p.PatientID = v.PatientID   INNER JOIN (     SELECT PatientID, MIN(VisitDate) VisitDate      FROM Visit      GROUP BY PatientID   ) f ON f.PatientID = p.PatientID AND f.VisitDate = v.VisitDate