Name the minimum kerry # for bush % for 50.9%
CREATE TABLE "by_county" (
  "county" text,
  "kerrypct" text,
  "kerrynum" real,
  "bushpct" text,
  "bushnum" real,
  "otherspct" text,
  "othersnum" real
);
SELECT MIN("kerrynum") FROM "by_county" WHERE "bushpct"='50.9%';