Sql Server 2008 MERGE - 获取计数的最佳方式

Question

我想知道你们会推荐什么作为从 Sql Server 中的 MERGE 语句中获取操作计数的最佳方法。

所以，即我运行一个 MERGE，它执行一些插入、一些更新和一些删除，...我希望能够找出多少插入、多少更新和多少删除。

最好的方法是什么？

Answer 1

要提取到单个变量中，可以通过 marc_s 使用 pivot 发布过程答案：

    declare
        @mergeResultsTable table (MergeAction VARCHAR(20));

    declare
        @insertCount int,
        @updateCount int,
        @deleteCount int;

    merge ...
    output $action into @mergeResultsTable; 

    select @insertCount = [INSERT],
           @updateCount = [UPDATE],
           @deleteCount = [DELETE]
      from (select 'NOOP' MergeAction -- row for null merge into null
             union all
            select * from @mergeResultsTable) mergeResultsPlusEmptyRow     
     pivot (count(MergeAction) 
       for MergeAction in ([INSERT],[UPDATE],[DELETE])) 
        as mergeResultsPivot;

如果 init vars 为 0 或知道源或目标表有 >0 行，则可以删除 union 'noop' 行。

Answer 2

怎么样：

INSERT YourResultsTable (action, cnt)
SELECT action, count(*)
FROM
(
    MERGE (targetTable) AS t 
    USING (sourceTable) AS s
       ON t.ID = s.ID
    WHEN MATCHED THEN      (some statements)
    WHEN NOT MATCHED THEN      (some statements)
    OUTPUT $action as action, inserted.ID as ins, deleted.ID as del
) m
GROUP BY action;

[编辑] 好的，那就试试吧：

INSERT YourResultsTable (action)
SELECT action
FROM
(
    MERGE (targetTable) AS t 
    USING (sourceTable) AS s
       ON t.ID = s.ID
    WHEN MATCHED THEN      (some statements)
    WHEN NOT MATCHED THEN      (some statements)
    OUTPUT $action as action, inserted.ID as ins, deleted.ID as del
) m;

（然后统计结果）

罗伯

Answer 3

您可以在 MERGE 语句中指定一个 OUTPUT 子句，并获得一份关于 MERGE 期间所做工作的输出报告。

MERGE (targetTable) AS t 
USING (sourceTable) AS s
ON t.ID = s.ID
WHEN MATCHED THEN
  (some statements)
WHEN NOT MATCHED THEN
  (some statements)
OUTPUT
  $action, inserted.ID 'inserted', deleted.ID 'deleted'
;

这将为每个操作的每个“操作”（插入、更新、删除）提供一行。如果语句很多，也可以 OUTPUT INTO @tableVar 然后查看表变量。

DECLARE @tableVar TABLE (MergeAction VARCHAR(20), InsertedID INT, DeletedID INT)

MERGE (targetTable) AS t 
USING (sourceTable) AS s
ON t.ID = s.ID
WHEN MATCHED THEN
      (some statements)
WHEN NOT MATCHED THEN
      (some statements)
OUTPUT
      $action, inserted.ID 'inserted', deleted.ID 'deleted' INTO @tableVar
;

SELECT MergeAction, COUNT(*) 
FROM @tableVar  
GROUP BY MergeAction

查看联机丛书以了解有关MERGE 声明和OUTPUT clause 的详细信息。

马克