CREATE TABLE "senate" (
  "state_class" text,
  "vacator" text,
  "reason_for_change" text,
  "successor" text,
  "date_of_successors_formal_installation" text
);

Question: How many reasons were given when A. Willis Robertson (D) resigned?
SQL: SELECT COUNT("reason_for_change") FROM "senate" WHERE "vacator"='A. Willis Robertson (D)';

Question: Who vacated his post when his successor was formally installed on May 11, 1966?
SQL: SELECT "vacator" FROM "senate" WHERE "date_of_successors_formal_installation"='May 11, 1966';

Question: What was the state (class) where the new successor was formally installed on May 11, 1966?
SQL: SELECT "state_class" FROM "senate" WHERE "date_of_successors_formal_installation"='May 11, 1966';