presto sql cross join 列转行问题

[jingyueYY]

select *,site_id from
(select distinct goods_sn,site_ids,split(site_ids, ',') array from prm
where goods_sn='abcdefg')
cross join unnest(array) t(site_id)

可以执行

select a.*,b.site_nm from
(select *,site_id from
(select distinct goods_sn,site_ids,split(site_ids, ',') array from prm
where goods_sn='abcdefg')
cross join unnest(array) t(site_id)) a left join
(select distinct site_id,site_nm from pub) b on a.site_id=b.site_id

就报错了，提示Column 'a.site_id' is ambiguous
怎么解决呢

[中国风]

参照方式：https://bbs.csdn.net/topics/240002706