Mysq updates its own table subquery, and the sorting is automatically incremented by 1

update  trade_goods_category a ,
(
select goods_cate_id,@rownum:= @rownum+1 as rownum   from trade_goods_category,(select @rownum:=0) t where parent_id in (select goods_cate_id from trade_goods_category where grade=1  and goods_cate_name ='铜') order by  parent_id,goods_cate_name

) b
set a.orders= b.rownum
where a.goods_cate_id =b.goods_cate_id