MYSQL中IFNULL的使用 以及统计2张表的字段和

SELECT SUM(total) as guess_right from (
select
IFNULL(ff_soccer_prize_knockout.guess_right_champion, 0) +
IFNULL(ff_soccer_prize_knockout.guess_right_strong8, 0) +
IFNULL(ff_soccer_prize_knockout.guess_right_strong4, 0) +
IFNULL(ff_soccer_prize_knockout.guess_right_strong2, 0) as total
from
ff_soccer_prize_knockout
where
playerid = '292578082'

UNION ALL

select
sum(guess_right) total from ff_soccer_prize
where
ff_soccer_prize.playerid = '292578082'
GROUP BY ff_soccer_prize.playerid
) c