select order_id,product_id,count(*)
from product_commit
group by order_id,product_id having count(*)>1

create table bak_product_comment_181119
as
select * from product_comment;
或者
create table bak_product_comment_181119
like product_comment;
 
//建立表結構
insert into bak_product_comment_181119
select * from product_comment;

delete a
from product_comment a
join(
select order_id,product_id,min(comment_id) as comment_id
from product_comment
group by order_id,product_id
having count(
 
*)>=2
) b on a.order_id=b.order_id and a.product_id=b.product_id
and a.comment_id > b.comment_id