CREATE TABLE table_38066 ("Outcome" TEXT, "Year" FLOAT, "Championship" TEXT, "Surface" TEXT, "Opponent" TEXT, "Score" TEXT)

Which championship has Roger Federer as an opponent on a clay surface in a year earlier than 2007?
SELECT "Championship" FROM table_38066 WHERE "Opponent" = 'roger federer' AND "Surface" = 'clay' AND "Year" < '2007'
SELECT "Championship" FROM "table_38066" WHERE "Opponent" = 'roger federer' AND "Surface" = 'clay' AND "Year" < '2007'