CREATE TABLE table_name_56 (year NUMBER, partnering VARCHAR2, championship VARCHAR2)

What year was the US Open that had a partnering of Maikel Scheffers?
SELECT SUM(year) FROM table_name_56 WHERE partnering = "maikel scheffers" AND championship = "us open"
SELECT SUM("year") FROM "table_name_56" WHERE "championship" = "us open" AND "maikel scheffers" = "partnering"