Who was the jockey with opening odds of 4-1?
CREATE TABLE "the_field" (
  "post" real,
  "horse_name" text,
  "trainer" text,
  "jockey" text,
  "opening_odds" text,
  "starting_odds" text,
  "finishing_pos" real
);
SELECT "jockey" FROM "the_field" WHERE "opening_odds"='4-1';