select a.campaign_id, a.tracklink_id - b.tracklink_id as diff from
(select campaign_id ,tracklink_id, @num := @num + 1 as row_number from (SELECT @num:=0) r,tab_campaign order by campaign_id) a,
(select campaign_id ,tracklink_id, @num2 := @num2 + 1 as row_number from (SELECT @num2:=0) r2, tab_campaign order by campaign_id) b
where a.row_number + 1 = b.row_number ;
