How many platforms have a southern opertator and the pattern is all stations via clapham junction?
CREATE TABLE "services" (
  "platform" real,
  "frequency_per_hour" real,
  "destination" text,
  "service_pattern" text,
  "operator" text,
  "line" text
);
SELECT COUNT("platform") FROM "services" WHERE "operator"='Southern' AND "service_pattern"='All stations via Clapham Junction';