CREATE TABLE "birthstones_by_cultures" (
  "month" text,
  "15th_20th_century" text,
  "u_s_1912" text,
  "u_s_2013" text,
  "britain_2013" text,
  "hindu" text
);

Question: What was Britain's (2013) birthstone when the U.S (2013) birthstone was ruby?
SQL: SELECT "britain_2013" FROM "birthstones_by_cultures" WHERE "u_s_2013"='ruby';

Question: What was the U.S birthstone in 1912 when in 2013 the birthstone was amethyst?
SQL: SELECT "u_s_1912" FROM "birthstones_by_cultures" WHERE "u_s_2013"='amethyst';

Question: What was the U.S birthstone in the 15th-20th century when in 2013 it was amethyst?
SQL: SELECT "15th_20th_century" FROM "birthstones_by_cultures" WHERE "u_s_2013"='amethyst';

Question: Which month in 2013 did the U.S. use the ruby birthstone?
SQL: SELECT "month" FROM "birthstones_by_cultures" WHERE "u_s_2013"='ruby';

Question: In 1912 when the U.S used sapphire, what was the Hindu birthstone?
SQL: SELECT "hindu" FROM "birthstones_by_cultures" WHERE "u_s_1912"='sapphire';