Name the least age 30-39 where age 20-29 is 593
CREATE TABLE "sterilization_operations_by_age_date" (
  "date_of_sterilization" text,
  "age_10_19" real,
  "age_20_29" real,
  "age_30_39" real,
  "age_40_49" real,
  "age_50_59" real,
  "age_unknown" real,
  "total" real
);
SELECT MIN("age_30_39") FROM "sterilization_operations_by_age_date" WHERE "age_20_29"=593;