CREATE TABLE table_name_46 (opponent VARCHAR2, surface VARCHAR2, date VARCHAR2)

Which Opponent has a Surface of hard on 28 august 1993?
SELECT opponent FROM table_name_46 WHERE surface = "hard" AND date = "28 august 1993"
SELECT "opponent" FROM "table_name_46" WHERE "28 august 1993" = "date" AND "hard" = "surface"