hapvlz

select 
    mon.mon_sid,
    mon.mon_hostname,
    mon.mon_port,
    mon.mon_display,
    logs_status AS current_status,
    previous_status,
    logs_updated
from (
    select 
        l.*,
        lag(logs_status) over(
            partition by mon_id
            order by logs_updated
        ) previous_status
    from logs l
) tmp
    INNER JOIN monitoring AS mon
    ON tmp.mon_id = mon.mon_id
where logs_status <> previous_status
ORDER BY logs_updated DESC