Currently, Dremio not support merge into with delete
but other engine (spark ) support
https://iceberg.apache.org/docs/latest/spark-writes/#merge-into
WHEN MATCHED AND s.op = 'delete' THEN DELETE
WHEN MATCHED AND t.count IS NULL AND s.op = 'increment' THEN UPDATE SET t.count = 0
WHEN MATCHED AND s.op = 'increment' THEN UPDATE SET t.count = t.count + 1