How many Podiums have a Class of 250cc, and an F laps of 0?
CREATE TABLE "by_season" (
  "year" text,
  "class" text,
  "team" text,
  "bike" text,
  "races" real,
  "wins" real,
  "podiums" real,
  "poles" real,
  "f_laps" real,
  "points" real
);
SELECT SUM("podiums") FROM "by_season" WHERE "class"='250cc' AND "f_laps"=0;