what is the total sack when totaltk is 1 and asst. is more than 0?
CREATE TABLE "defense" (
  "player" text,
  "tackles" real,
  "asst" real,
  "total_tk" real,
  "sack" real,
  "yards" real,
  "fum_r" real
);
SELECT SUM("sack") FROM "defense" WHERE "total_tk"=1 AND "asst">0;