CREATE TABLE table_79307 ("Year" FLOAT, "Competition" TEXT, "Venue" TEXT, "Position" TEXT, "Notes" TEXT)

Which Notes have a Competition of world championships, and a Position of 2nd?
SELECT "Notes" FROM table_79307 WHERE "Competition" = 'world championships' AND "Position" = '2nd'
SELECT "Notes" FROM "table_79307" WHERE "Competition" = 'world championships' AND "Position" = '2nd'