從有多個事件的表中獲取唯一記錄

Question

我試圖拉起所有患者記錄（沒有重複）。在我的數據庫中，所有患者都有多個訪問ID和多個訪問日期。

我已經試過這一個：

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

Answer 1

試試這個。

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