SQL Server 中单行 MERGE / upsert 的语法

Question

我正在尝试对表进行单行插入/更新，但所有示例都是针对集合的。

谁能修正我的语法：

MERGE member_topic ON mt_member = 0 AND mt_topic = 110
WHEN MATCHED THEN UPDATE SET mt_notes = 'test'
WHEN NOT MATCHED THEN INSERT (mt_member, mt_topic, mt_notes) VALUES (0, 110, 'test')

每个 marc_s 的解决方案是将单行转换为子查询 - 这让我认为 MERGE 命令并不是真正适用于单行 upserts。

MERGE member_topic
USING (SELECT 0 mt_member, 110 mt_topic) as source
ON member_topic.mt_member = source.mt_member AND member_topic.mt_topic = source.mt_topic
WHEN MATCHED THEN UPDATE SET mt_notes = 'test'
WHEN NOT MATCHED THEN INSERT (mt_member, mt_topic, mt_notes) VALUES (0, 110, 'test');

Answer 1

我终于在 SQL Server 2008 中使用 MERGE 获得了 Upsert 语法。使用 Jacob想要 做的事情（一个 Upsert）：

IF EXISTS(SELECT * FROM member_topic WHERE mt_member = 0 AND mt_topic = 110)
BEGIN
    --update existing row
    UPDATE member_topic SET mt_notes = 'test'
    WHERE mt_member = 0
    AND mt_topic = 110
END
ELSE
BEGIN
    --insert new row
    INSERT INTO member_topic (mt_member, mt_topic, mt_notes)
    VALUES (0, 110, 'test')
END

等价的MERGE语法是：

MERGE member_topic
USING ( 
    VALUES (0, 110, 'test')
) AS foo (mt_member, mt_topic, mt_notes) 
ON member_topic.mt_member = foo.mt_member 
   AND member_topic.mt_topic = foo.mt_topic
WHEN MATCHED THEN
   UPDATE SET mt_notes = foo.mt_notes
WHEN NOT MATCHED THEN
   INSERT (mt_member, mt_topic, mt_notes)
   VALUES (foo.mt_member, foo.mt_topic, foo.mt_notes)
; --A MERGE statement must be terminated by a semi-colon (;).

Answer 2

基本上，您在正确的轨道上 - 但是您缺少要合并数据的来源 - 尝试这样的事情：

MERGE 
   member_topic AS target
USING 
   someOtherTable AS source
ON 
   target.mt_member = source.mt_member 
   AND source.mt_member = 0 
   AND source.mt_topic = 110
WHEN MATCHED THEN 
   UPDATE SET mt_notes = 'test'
WHEN NOT MATCHED THEN 
   INSERT (mt_member, mt_topic, mt_notes) VALUES (0, 110, 'test')
; 

单行 MERGE 没有特殊的语法 - 您需要做的就是使用适当的子句。使用ON 子句中的适当条件，您可以将源限制为单行 - 没问题。

不要忘记结尾的分号！不开玩笑 - 这很重要！

请参阅this blog post 了解MERGE 的真正介绍。