In SQL Server 2012,
Does a merge statement like this :
WHEN MATCHED THEN update SET A.len = B.len
updates a row even if A.len equals to B.len ?
Or does the SQL SERVER knows to ignore this situations ?
If not, would it be better to add the matching condition the following :
WHEN MATCHED AND A.len <> B.len THEN update SET A.len = B.len
Is there any difference in this on other Sql servers ?