CREATE TABLE table_204_511 (id NUMBER, "number" NUMBER, "driver" CLOB, "entrant" CLOB, "chassis" CLOB, "engine" CLOB, "tyre" CLOB)

what was the only engine used one time ?
SELECT "engine" FROM table_204_511 GROUP BY "engine" HAVING COUNT(*) = 1
SELECT "engine" FROM "table_204_511" GROUP BY "engine" HAVING COUNT(*) = 1