What chng has a rank greater than 6, with 12 as a prev?
CREATE TABLE "fide_april_2008_top_ten" (
  "rank" real,
  "prev" real,
  "player" text,
  "rating" real,
  "chng" text
);
SELECT "chng" FROM "fide_april_2008_top_ten" WHERE "rank">6 AND "prev"=12;