What is Replaced By, when Date of Vacancy is "23 February 2009"?
CREATE TABLE "managerial_changes" (
  "team" text,
  "outgoing_manager" text,
  "manner_of_departure" text,
  "date_of_vacancy" text,
  "replaced_by" text,
  "date_of_appointment" text
);
SELECT "replaced_by" FROM "managerial_changes" WHERE "date_of_vacancy"='23 february 2009';