Question

最初我尝试使用IF / ELSE来完成＆＃34; UPSERT＆＃34;并且有人建议我使用MERGE我MERGE的问题，看起来我不能使用两个来源。

这是我原创的尝试：

IF ((SELECT COUNT(CAST(StudentuserID AS int)) FROM HL_StudentAttendance WHERE StudentUserID=1)>0)
UPDATE HL_StudentAttendance
SET
CID = CAST('[querystring:CID]' AS int),
CalendarEventID = CAST('[querystring:CEID]' AS int),
StudentUserID = CAST('[StudentUserID]' AS int),
Attendance = '[Attendance]'
ELSE
INSERT INTO HL_StudentAttendance
(CID,CalendarEventID,StudentUserID,Attendance)
VALUES
(CAST('[querystring:CID]' AS int), CAST('[querystring:CEID]' AS int), CAST('[StudentsUserID]' AS int),'[Attendance]')

即使IF语句结果是8所以8>0它应该运行我的更新，它总是运行一个插入，不确定我的if / else逻辑是否遗漏了什么。

以下是MERGE

的尝试

MERGE 
   HL_StudentAttendance AS target
USING 
   HL_CourseRegistrations AS source
ON 
   target.StudentUserID = source.UserID
   AND source.
WHEN MATCHED THEN 
   UPDATE SET 
   Attendance = '[Attendance]'
WHEN NOT MATCHED THEN 
   INSERT (CID, CalendarEventID, StudentUserID, Attendance) VALUES ('[querystring:CID]', '[querystring:CEID]', '[UserID]', '[Attendance]')
;

我的问题是我的表HL_CourseEvents中有数据应该用于获取CalendarEventID的其他源项，否则MERGE可以工作，但会在我的{{{}}中插入重复的条目{1}}因为HL_StudentAttendance

没有参数

任何建议表示赞赏。

更新

以下查询确实有效，但如果在出勤字段上更改了任何内容而不是正确更新，则会插入新记录。我怀疑因为我的更新中的WHERE子句不存在。我尝试添加它导致执行错误

CalendarEventID

查询结果运行两次。如果我继续运行它，它将始终插入更多而不是更新：

MERGE HL_StudentAttendance
USING
(
SELECT cr.CID, ce.CalendarEventID, cr.UserID FROM HL_CourseRegistrations cr
JOIN HL_CalendarEvents ce
ON ce.CID = cr.CID
) tmpTable
ON
HL_StudentAttendance.StudentUserID = tmpTable.UserID
AND HL_StudentAttendance.CalendarEventID = tmpTable.CalendarEventID
WHEN MATCHED THEN
UPDATE
SET
Attendance = 'Attended Late'
WHEN NOT MATCHED THEN 
INSERT (CID,CalendarEventID,StudentUserID,Attendance) VALUES ('1','1','1','555')
;

Answer 1

根据其他信息，请尝试以下操作。我已经将模式和一些数据混合在一起仅用于演示目的，因此您必须了解模式的比较方式。然而，底部的两个例子做了我相信的问题。如果根据用户ID不存在，则第一个插入新记录。第二个标志记录为＆＃34;参加晚期＆＃34;如果它存在请注意，对于现实生活，您可能需要多个参数，因为用户可以注册多个课程，因此您也希望传递课程或日历事件ID。如果这让你开始或者你需要额外的东西，请告诉我。

--
-------------------------------------------------
CREATE TABLE [test].[HL_StudentAttendance]
  (
       [StudentUserID]     INT
       , [CalendarEventID] INT
       , [Attendance]      NVARCHAR(250)
       , [CID]             INT
  );

CREATE TABLE [test].[HL_CourseRegistrations]
  (
       [CID]      INT
       , [UserID] INT
  );

CREATE TABLE [test].[HL_CalendarEvents]
  (
       [CalendarEventID] INT
       , [CID]           INT
  );

go

--
-------------------------------------------------
INSERT INTO [test].[HL_CourseRegistrations]
            ([CID]
             , [UserId])
VALUES      (1,1),
            (3,4),
            (4,5);

INSERT INTO [test].[HL_CalendarEvents]
            ([CalendarEventID]
             , [CID])
VALUES      (1,1);

go

--
-------------------------------------------------
CREATE PROCEDURE [test].[set_attendance] @user INT
AS
    BEGIN
        MERGE INTO [test].[HL_StudentAttendance] AS [target]
        USING (SELECT [cr].[CID]
                      , [ce].[CalendarEventID]
                      , [cr].[UserID]
               FROM   [test].[HL_CourseRegistrations] [cr]
                      JOIN [test].[HL_CalendarEvents] [ce]
                        ON [ce].[CID] = [cr].[CID]) AS [source]
        ON [target].[StudentUserID] = @user
           AND [target].[CalendarEventID] = [source].[CalendarEventID]
        WHEN MATCHED THEN
            UPDATE SET [Attendance] = 'Attended Late'
        WHEN NOT MATCHED BY target THEN
            INSERT ([CID]
                    , [CalendarEventID]
                    , [StudentUserID]
                    , [Attendance])
            VALUES ('1'
                    , '1'
                    , @user
                    , '555');
    END;

go

--
-- inserts a new record
-------------------------------------------------
EXECUTE [test].[set_attendance]
    @user=12;

SELECT *
FROM   [test].[HL_StudentAttendance];


--
-- marks an existing record as late
-------------------------------------------------
EXECUTE [test].[set_attendance]
    @user=12;

SELECT *
FROM   [test].[HL_StudentAttendance];

TSQL MERGE具有多个来源

1 个答案: