with t as (select 订单号,商品号,支付金额,包裹号,总运费,商品类型 from 订单表
join 运费表 using(订单号,商品号)
join 品类表 using(商品号))

select 商品类型,sum(支付金额) as 支付金额, sum(总运费) as 总运费, sum(总运费)/sum(支付金额) as 运费占比 from t
group by 商品类型