What is the Men's 35 in year before 1990 when Men's Open is NSW and the venue is Sydney?
CREATE TABLE "results_of_the_national_championships_19" (
  "year" real,
  "venue" text,
  "men_s_open" text,
  "women_s_open" text,
  "men_s_35s" text
);
SELECT "men_s_35s" FROM "results_of_the_national_championships_19" WHERE "year"<1990 AND "men_s_open"='nsw' AND "venue"='sydney';