Example
MERGE INTO targetTable t
USING sourceTable s
ON t.PKID = s.PKID
WHEN MATCHED AND NOT EXISTS (
SELECT s.ColumnA, s.ColumnB, s.ColumnC
INTERSECT
SELECT t.ColumnA, t.ColumnB, s.ColumnC
)
THEN UPDATE SET
t.ColumnA = s.ColumnA
,t.ColumnB = s.ColumnB
,t.ColumnC = s.ColumnC
WHEN NOT MATCHED BY TARGET
THEN INSERT (PKID, ColumnA, ColumnB, ColumnC)
VALUES (s.PKID, s.ColumnA, s.ColumnB, s.ColumnC)
WHEN NOT MATCHED BY SOURCE
THEN DELETE
;
Note: The AND NOT EXISTS portion prevents updating records that haven't changed. Using the INTERSECT construct allows nullable columns to be compared without special handling.
