An excellent primer on the MERGE statement, thank you.

Please can I point out what I believe is simply an inadvertent typo on your part? Re listing 4 you state:

"This clause tells SQL Server whenever it finds a record in the “Source” table that is not contained in the target table that it needs to perform a DELETE operation."

This should be the other way around i.e. when record is found in Target table that is not found in Source.

Great article, thanks again