1，一行转多行
url列以分号分隔，将其一行转化为多行，借助自增长表help_topic 实现。
select a.channel_id,channel_code,site_name,siteid,refer_channel,substring_index(substring_index(a.url,';',b.help_topic_id+1),';',-1) as urls from t_channel_mapping a join mysql.help_topic b on (length(a.url) - length(replace(a.url,';',''))+1) > b.help_topic_id;
2，多行转一行
分组后汇总成一行，orderid以逗号分隔
select SiteID,group_concat(distinct cast(orderid as char(8))) as orderid from site_order
3，Mysql实现rownumber
mysql是不支持rownum函数，下面例子实现产品表中给产品一个顺序编号
select @rownum:=@rownum+1 rownum, product
from
(
select (@rownum:=0),a.product
from
(select product from t_proudct_info GROUP BY product) a
) t