When the 2006  census had a population of 422204, what was the density (pop/km²) ?
CREATE TABLE "references" (
  "name" text,
  "2011_census" real,
  "2006_census" real,
  "pct_change" text,
  "land_area_km" text,
  "density_pop_km" text,
  "population_rank" real
);
SELECT COUNT("density_pop_km") FROM "references" WHERE "2006_census"=422204;