What is the total number of Post, when Trainer is "Steve Asmussen", and when Time/ Behind is 19 ½?
CREATE TABLE "post_positions" (
  "finished" real,
  "time_behind" text,
  "post" real,
  "horse" text,
  "jockey" text,
  "trainer" text,
  "owner" text
);
SELECT COUNT("post") FROM "post_positions" WHERE "trainer"='steve asmussen' AND "time_behind"='19 ½';