CREATE TABLE "past_winners" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);

Question: Who won Women's doubles when Raina Tzvetkova won women's singles before 2000?
SQL: SELECT "women_s_doubles" FROM "past_winners" WHERE "year"<2000 AND "women_s_singles"='raina tzvetkova';

Question: Who won men's singles when petya nedelcheva diana dimova won women's doubles and vladimir metodiev krasimir yankov won men's doubles?
SQL: SELECT "men_s_singles" FROM "past_winners" WHERE "women_s_doubles"='petya nedelcheva diana dimova' AND "men_s_doubles"='vladimir metodiev krasimir yankov';

Question: Who won men's singles when petya nedelcheva won women's singles, petya nedelcheva diana dimova won women's doubles, stilian makarski diana dimova won mixed doubles, and stilian makarski peyo boichinov won men's doubles?
SQL: SELECT "men_s_singles" FROM "past_winners" WHERE "women_s_singles"='petya nedelcheva' AND "women_s_doubles"='petya nedelcheva diana dimova' AND "mixed_doubles"='stilian makarski diana dimova' AND "men_s_doubles"='stilian makarski peyo boichinov';

Question: Who won women's singles in 1986?
SQL: SELECT "women_s_singles" FROM "past_winners" WHERE "year"=1986;