What number of completions are recorded for the year with 12 games started?
CREATE TABLE "career_statistics" (
  "year" real,
  "games" real,
  "games_started" real,
  "completions" real,
  "attempts" real,
  "completion_pct" text,
  "yards" real,
  "yards_attempt" text,
  "touchdowns" real,
  "interceptions" real,
  "rating" text
);
SELECT "completions" FROM "career_statistics" WHERE "games_started"=12;