CREATE TABLE table_203_539 (id NUMBER, "year" NUMBER, "competition" CLOB, "venue" CLOB, "position" CLOB, "event" CLOB, "notes" NUMBER)

what distance hurdles was run the most ?
SELECT "event" FROM table_203_539 GROUP BY "event" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "event" FROM "table_203_539" GROUP BY "event" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY