CREATE TABLE "current_fleet_details" (
  "class" text,
  "operator" text,
  "no_built" real,
  "year_built" text,
  "cars_per_set" real,
  "unit_nos" text
);

Question: What year was number 7 built?
SQL: SELECT "year_built" FROM "current_fleet_details" WHERE "no_built"=7;