Error ->
SELECT *
FROM (
SELECT *, @RNUM := @RNUM + 1 AS RNUM
FROM board_list, (SELECT @RNUM := 0) A
WHERE 1=1
and Scod = 'BRD01' order by b_notice ASC, b_ref DESC, b_step ASC, seq DESC
)b
WHERE RNUM <
ORDER BY RNUM DESC
LIMIT 1