CREATE TABLE table_name_74 (year INT, opponent_in_the_final VARCHAR)

How many years have an Opponent in the final of welby van horn?
SELECT SUM(year) FROM table_name_74 WHERE opponent_in_the_final = "welby van horn"
SELECT SUM("year") FROM "table_name_74" WHERE "opponent_in_the_final" = "welby van horn"