CREATE TABLE table_62013 ("Outcome" CLOB, "Edition" FLOAT, "Round" CLOB, "Opponent Team" CLOB, "Surface" CLOB, "Opponent" CLOB, "Score" CLOB)

What is Opponent, when Round is World Group?
SELECT "Opponent" FROM table_62013 WHERE "Round" = 'world group'
SELECT "Opponent" FROM "table_62013" WHERE "Round" = 'world group'