CREATE TABLE "class_253_and_254" (
  "class" text,
  "operator" text,
  "number" real,
  "year_built" text,
  "cars_per_set" real,
  "unit_numbers" text
);

Question: What is the smallest number for Cars per Set built in 1977-1979 larger than 32?
SQL: SELECT MIN("cars_per_set") FROM "class_253_and_254" WHERE "year_built"='1977-1979' AND "number">32;

Question: What unit has cars per set larger than 9 built in 1982?
SQL: SELECT "unit_numbers" FROM "class_253_and_254" WHERE "cars_per_set">9 AND "year_built"='1982';

Question: What is the largest number of cars per set that is less than 9?
SQL: SELECT MAX("number") FROM "class_253_and_254" WHERE "cars_per_set"<9;

Question: What year was the class 253 larger than 18 built?
SQL: SELECT "year_built" FROM "class_253_and_254" WHERE "class"='class 253' AND "number">18;