CREATE TABLE table_203_28 (id NUMBER, "year" NUMBER, "competition" CLOB, "venue" CLOB, "position" CLOB, "event" CLOB, "notes" CLOB)

how many years consecutive featured the 20 km event ?
SELECT COUNT(DISTINCT "year") FROM table_203_28 WHERE "event" = '20 km'
SELECT COUNT(DISTINCT "year") FROM "table_203_28" WHERE "event" = '20 km'