what is the length (miles) when the name is l-56g?
CREATE TABLE "connecting_links" (
  "county" text,
  "name" text,
  "length_miles" real,
  "west_or_south_terminus" text,
  "east_or_north_terminus" text
);
SELECT MAX("length_miles") FROM "connecting_links" WHERE "name"='l-56g';