第一种方式demo:
$sql = "select
g.name,
b.name as b.goods_name
from
`demo`
left join `goods` as g on demo.id=g.goods_id
left join `goods` as b on demo.child_id=b.goods_id";
第二种方式demo：
$sql = "select
c.*,
b.name as goods_name
from (
select
id,
child_id,
g.name
from
`demo`
left join `goods` as g on demo.id=g.goods_id) as c
left join `goods` as b on c.child_id=b.goods_id
";