você deve usar uma mesclar declaração
algo assim:
merge TableMain AS target
using TableA as source
ON <join tables here>
WHEN MATCHED THEN <update>
WHEN NOT MATCHED BY TARGET <Insert>
WHEN NOT MATCHED BY SOURCE <delete>
merge TableMain AS target
using TableA as source
ON <join tables here>
WHEN MATCHED THEN <update>
WHEN NOT MATCHED BY TARGET <Insert>
WHEN NOT MATCHED BY SOURCE <delete>
