将插入与选择语句合并

Question

这对我有用

MERGE Table1 AS tgt
USING
(
    SELECT
        TOP 1
        *
    FROM
        Table2,
        (
            SELECT
                itmid
            FROM
                Table3
            WHERE
                id = @id
        ) as a
    WHERE
        id = @id
) AS src
ON ( tgt.id = src.id )
WHEN MATCHED THEN
    UPDATE SET qty = qty + @qty
WHEN NOT MATCHED THEN
    INSERT itmid
    VALUES itmid;

但是当我这样改变时，它不起作用，在最后一个 select 附近显示错误

MERGE Table1 AS tgt
USING
(
    SELECT
        TOP 1
        *
    FROM
        Table2
    WHERE
        id = @id
) AS src
ON ( tgt.id = src.id )
WHEN MATCHED THEN
    UPDATE SET qty = qty + @qty
WHEN NOT MATCHED THEN
    INSERT itmid
    SELECT itmid FROM Table3 WHERE id = @id;

Answer 1

根据MSDN docs

<merge_not_matched>::=
{
    INSERT [ ( column_list ) ] 
        { VALUES ( values_list )
        | DEFAULT VALUES }
}

INSERT 的语法 来自 SELECT like:

  WHEN NOT MATCHED THEN
            INSERT itmid SELECT itmid FROM Table3 WHERE id=@id;

不允许！

我会尝试通过与Table3 再次合并来解决您的问题。

Answer 2

这样做

 MERGE Table1 AS tgt
 USING (SELECT TOP 1 * FROM Table2
        WHERE id = @id) AS src
ON (tgt.id = src.id)
            WHEN MATCHED THEN UPDATE SET qty = qty + @qty
            WHEN NOT MATCHED THEN
                INSERT (itmid) 
                 SELECT itmid FROM Table3 WHERE id=@id;

根据http://msdn.microsoft.com/en-us/library/bb522522(v=sql.105).aspx应该可以正常工作

对不起，我解释错了，我原来的答案是

MERGE Table1 AS tgt
     USING (SELECT TOP 1 * FROM Table2
            WHERE id = @id) AS src
    ON (tgt.id = src.id)
                WHEN MATCHED THEN UPDATE SET qty = qty + @qty
                WHEN NOT MATCHED THEN
                    INSERT (itmid) values (SELECT top 1 itmid FROM Table3 WHERE id=@id);

由于合并插入一次需要一个插入，并且多次插入可能会失败。