What is the total difference for teams that played less than 6 games?
CREATE TABLE "europe_pool_a" (
  "club" text,
  "played" real,
  "lost" real,
  "drawn" real,
  "against" real,
  "diff" real,
  "points" real
);
SELECT SUM("diff") FROM "europe_pool_a" WHERE "played"<6;