sql-server - SQL合并错误: The MERGE statement attempted to UPDATE or DELETE

Question

我有一个源表

select 54371 Id, 'foo' [CreateBy], '2016-10-24 09:29:18.548'[CreateDate], 'foo'[UpdateBy],  '2016-10-24 09:29:18.548'[UpdateDate], 'E'[MT], 185761[MID], 3[BGID]
union
select 54372, 'foo', '2016-10-24 09:30:18.548', 'foo',  '2016-10-24 09:30:18.548',  'E', 185761, 2

和目标表

select 54379 Id, 'foo' [CreateBy], '2016-10-24 09:29:18.548'[CreateDate], 'foo'[UpdateBy],  '2016-10-24 10:29:18.548'[UpdateDate], 'E'[MT], 185761[MID], 3[BGID]

我想要的是基于MT、MID进行匹配

1. 如果不存在则插入
2. 如果 BGID 匹配则更新
3. 如果 BGID 不匹配则删除

当我使用 SQL 合并语句时出现错误

The MERGE statement attempted to UPDATE or DELETE the same row more than once. This happens when a target row matches more than one source row. A MERGE statement cannot UPDATE/DELETE the same row of the target table multiple times. Refine the ON clause to ensure a target row matches at most one source row, or use the GROUP BY clause to group the source rows.`

我的合并是这样的

MERGE   
  FooBar AS target
USING
(
SELECT
E.[Id],
E.[CreateBy],
E.[CreateDate],
E.[UpdateBy],
E.[UpdateDate],
E.[MT],
E.[MID],
E.[BGID]
FROM @FooBar E
) AS source
ON
source.MID = target.MID
AND source.MT = target.MT
WHEN MATCHED and target.[BGID] = source.[BGID] THEN
UPDATE SET
target.[UpdateBy] = Source.[UpdateBy]
,target.[UpdateDate] = Source.[UpdateDate]
When Matched and source.BGID <> target.BGID THEN
DELETE
WHEN NOT MATCHED THEN
INSERT([CreateBy]
,[CreateDate]
,[UpdateBy]
,[UpdateDate]
,[MT]
,[MID]
,[BGID])
VALUES
(
Source.[CreateBy]
,Source.[CreateDate]
,Source.[UpdateBy]
,Source.[UpdateDate]
,Source.[MT]
,Source.[MID]
,Source.[BGID]
);

我错过了什么？

Answer 1

您正在加入 ON source.MappingId = target.MappingId 上的表。

在您的数据示例中，有超过 1 行具有相同的 MappingId = 185761。 所以你得到了:

A MERGE statement cannot UPDATE/DELETE the same row of the target table multiple times.

您需要指定一些唯一的列组合来连接源和目标表。