CREATE TABLE table_204_498 (id NUMBER, "location" CLOB, "building" CLOB, "year" NUMBER, "km" NUMBER, "monument" NUMBER)

what km comes after 8.25 , but before
SELECT "km" FROM table_204_498 WHERE id = (SELECT id FROM table_204_498 WHERE "km" = 8.25) + 1
SELECT "km" FROM "table_204_498" WHERE "id" = (SELECT "id" FROM "table_204_498" WHERE "km" = 8.25) + 1