MERGE INTO TargetTable AS Target
USING (VALUES (1,'Value1'), (2, 'Value2'), (3,'Value3'))
AS Source (PKID, ColumnA)
ON Target.PKID = Source.PKID
WHEN MATCHED THEN
UPDATE SET target.ColumnA= source.ColumnA
WHEN NOT MATCHED THEN
INSERT (PKID, ColumnA) VALUES (Source.PKID, Source.ColumnA);