CREATE TABLE "table1_28688313_1" (
  "num" real,
  "episode" text,
  "directed_by" text,
  "written_by" text,
  "u_s_viewers_in_millions" text,
  "original_airdate" text
);

Question: Who wrote the episode with 7.52 million US viewers?
SQL: SELECT "written_by" FROM "table1_28688313_1" WHERE "u_s_viewers_in_millions"='7.52';

Question: What are the titles of episodes numbered 19?
SQL: SELECT "episode" FROM "table1_28688313_1" WHERE "num"=19;

Question: Who wrote the episode with 9.81 million US viewers?
SQL: SELECT "written_by" FROM "table1_28688313_1" WHERE "u_s_viewers_in_millions"='9.81';