CREATE TABLE table_name_15 (date VARCHAR2, surface VARCHAR2, score VARCHAR2)

What is the date of the match on clay with score of 6-3 2-6 6-4?
SELECT date FROM table_name_15 WHERE surface = "clay" AND score = "6-3 2-6 6-4"
SELECT "date" FROM "table_name_15" WHERE "6-3 2-6 6-4" = "score" AND "clay" = "surface"