Question: On what date was James P. Buchanan (D)'s successor seated?
SQL: SELECT "Date successor seated" FROM "1-2159547-3" WHERE "Vacator" = 'James P. Buchanan (D)';

Question: How many people vacated to successor Dave E. Satterfield, Jr. (D)?
SQL: SELECT COUNT("Vacator") FROM "1-2159547-3" WHERE "Successor" = 'Dave E. Satterfield, Jr. (D)';

Question: Why did Robert L. Bacon (R) vacate?
SQL: SELECT "Reason for change" FROM "1-2159547-3" WHERE "Vacator" = 'Robert L. Bacon (R)';