根據處理方式不同：
select a.*,if(@tmp=CONCAT(r_content,r_userid),@rownum:=@rownum+1,@rownum:=1) as rownum,@tmp:=CONCAT(r_content,r_userid) from (
select a.* from reviews a INNER JOIN
(select r_content,r_userid,count(*) from reviews GROUP BY r_content,r_userid having count(*)>1 ) b
on a.r_content=b.r_content and a.r_userid=b.r_userid ) a,(select @rownum:=0,@tmp:='') b
delete from xxx where r_id in
或者
select GROUP_CONCAT(r_id) as ids,r_content,r_userid,count(*) from reviews GROUP BY r_content,r_userid
HAVING count(*)>1