CREATE TABLE table_42540 ("Result" TEXT, "Opponent" TEXT, "Type" TEXT, "Round" TEXT, "Date" TEXT)

Which Opponent has a Type of tko, and a Round of 2 (6) on 2006-09-20?
SELECT "Opponent" FROM table_42540 WHERE "Type" = 'tko' AND "Round" = '2 (6)' AND "Date" = '2006-09-20'
SELECT "Opponent" FROM "table_42540" WHERE "Date" = '2006-09-20' AND "Round" = '2 (6)' AND "Type" = 'tko'