从有多个事件的表中获取唯一记录

Question

我试图拉起所有患者记录（没有重复）。在我的数据库中，所有患者都有多个访问ID和多个访问日期。

我已经试过这一个：

SELECT DISTINCT * 
FROM PatientVisit 
WHERE Visit IN (SELECT MIN(Visit) FROM PatientVisit GROUP BY PatientProfileId) 

Answer 1

试试这个。

SELECT 
    DISTINCT VisitMain.PatientID 
    ,MaxVisit.FirstVisit 
    ,MinVisit.LastVisit 
FROM 
    PatientVisit VisitMain (NOLOCK) 
LEFT JOIN 
    (SELECT 
     PatientID,FirstVisit = MAX(CONVERT(DATETIME,Visit)) 
    FROM 
     PatientVisit (NOLOCK) 
    GROUP BY 
     PatientID) MaxVisit 
ON VisitMain.PatientID = MaxVisit.PatientID 
LEFT JOIN 
    (SELECT 
     PatientID,LastVisit = MIN(CONVERT(DATETIME,Visit)) 
    FROM 
     PatientVisit (NOLOCK) 
    GROUP BY 
     PatientID) MinVisit 
ON VisitMain.PatientID = MinVisit.PatientID