mysql存储过程中如何求出数据表统计列所占百分比

Question

数据表
name brand_id goods_num
回力 1         2
耐克 2         2
回力 1         1目标结果集是 
name brand_id goods_num_rate
回力 1         60%
耐克 2         40%goods_num总共有5个，回力有3个那么 占比例为20%，同理，耐克2个占40%

Answer 1

select name,brand_id,concat(sm1*100/sm2,'%') goods_num_rate from 
(select name,brand_id,sum(goods_num) sm1
from tab 
group by name,brand_id) a,
(select sum(goods_num) sm2 from tab) b
;

Answer 2

select name,brand_id, sum(goods_num)/(select sum(goods_num) from 数据表)
from 数据表 
group by name,brand_id