How many partners were there when the score was 7–6 (7–4) , 6–3?
CREATE TABLE "doubles_7_3_4" (
  "outcome" text,
  "year" real,
  "championship" text,
  "surface" text,
  "partner" text,
  "opponents" text,
  "score" text
);
SELECT COUNT("partner") FROM "doubles_7_3_4" WHERE "score"='7–6 (7–4) , 6–3';