What's the version that has a 20.0 mbit/s downstream rate?
CREATE TABLE "adsl_standards" (
  "version" text,
  "standard_name" text,
  "common_name" text,
  "downstream_rate" text,
  "upstream_rate" text
);
SELECT "version" FROM "adsl_standards" WHERE "downstream_rate"='20.0 mbit/s';