syntax for single row MERGE / upsert in SQL Server

Question

I'm trying to do a single row insert/update on a table but all the examples out there are for sets.

Can anyone fix my syntax please:

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')

Resolution per marc_s is to convert the single row to a subquery - which makes me think the MERGE command is not really intended for single row 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

Basically, you're on the right track - but you're missing a source from where you want to merge the data - try something like this:

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')
; 

There is no special syntax for a single row MERGE - all you need to do is use a proper clause. With that proper condition in the ON clause, you can limit the source to a single row - no problem.

And don't forget the trailing semicolon! No joke - it's important!

See this blog post for a really good intro to MERGE.