Question

我正在尝试学习如何使用MERGE运算符。以下代码正确编译：

    ALTER PROCEDURE moto.procPM_UpdateLines
@LineId As Int = null,
@LineName As Varchar(100),
@DeleteMe As Bit = 0
    AS
    BEGIN

    MERGE moto.tblPMLine AS line
    USING (SELECT LineId, LineName FROM moto.tblPMLine) AS existsLine
    ON line.LineId = existsLine.LineId
    WHEN MATCHED AND @DeleteMe = 1 THEN DELETE
    WHEN MATCHED AND @DeleteMe = 0 THEN UPDATE SET line.LineName = @LineName
    WHEN NOT MATCHED THEN INSERT(LineName) VALUES(@LineName);
    END
    GO

这是一个非常简单的过程，我知道，但由于某种原因，当我使用以下命令时它似乎没有生成任何条目。

    execute moto.procPM_UpdateLines null, 'First test', 0

有没有办法让我知道它所遵循的选项，如果有的话？

以前的存储过程已修复。

   MERGE INTO moto.tblPMLine AS T
   USING (SELECT @LineId as LineId, @LineName as LineName) AS S
   ON T.LineId = S.LineId
   WHEN MATCHED AND @DeleteMe = 0 THEN --UPDATE
        UPDATE SET LineName = @LineName 
   WHEN MATCHED AND @DeleteMe = 1 THEN --DELETE
        DELETE
   WHEN NOT MATCHED THEN--INSERT
        INSERT (LineName) VALUES (@LineName)    
   OUTPUT $action AS ChangesMade;

现在它插入，更新和删除，以及返回输出。

Answer 1

您可以合并MERGE和OUTPUT子句来获取MERGE正在做的某种“活动报告”（或调试“打印报表”） - 也许是将帮助您了解出现问题的原因。

参见Adam Machanic的优秀博客文章Dr. OUTPUT or: How I Learned to Stop Worrying and Love the MERGE，其中显示了该技术以及如何使用它

基本上归结为使用OUTPUT子句和MERGE语句来获取有关正在发生的事情的信息 - 大致类似于：

MERGE INTO ......
WHEN MATCHED THEN
    .......
WHEN NOT MATCHED THEN
    ......
WHEN NOT MATCHED BY SOURCE THEN
    ........
OUTPUT
    $action AS dml_action,
    inserted.x AS new_x,
    deleted.x AS old_x,
    inserted.y AS new_y,
    deleted.y AS old_y;

Answer 2

MERGE moto.tblPMLine AS line
USING (SELECT LineId, LineName FROM moto.tblPMLine WHERE LineID = @LineID) AS existsLine

请原谅我，因为我没有使用MERGE。但是，我没有看到使用@LineID变量的代码。

如何在SQL Server中调试合并？

2 个答案: