1、把结果按分组用逗号分割，以一行打印出来。（如果需要换其它的可以用replace函数：replace(wm_concat(name),',','|')）
select t.u_id,
wmsys.wm_concat(t.goods),
wmsys.wm_concat(t.goods || '(' || t.u_id || '斤)')
from tb_index t
group by t.u_id;
2、over(partition by t.u_id)用法：
select t.u_id,
wmsys.wm_concat(t.goods || '(' || t.u_id || '斤)') over(partition by t.u_id)
from tb_index t;
3、over(order by t.u_id)用法：
select t.u_id,
wmsys.wm_concat(t.goods || '(' || t.u_id || '斤)') over(partition by t.u_id)
from tb_index t;
4、懒人扩展用法:（大表很多字段我需要串起来）
select 'select '|| wm_concat('t.'||column_name) || ' from TB_INDEX t' from user_tab_columns where table_name='TB_INDEX';
sys_connect_by_path(columnname, seperator) ：用来构造树路径的，所以需要和connect by一起来用。
sys_connect_by_path 函数主要作用是可以把一个父节点下的所有子节点通过某个字符进行区分，然后连接在一个列中显示
select t.areaid,
t.parentareaid,
t.areaname,
sys_connect_by_path(t.areaname, '-') area
from tb_index t
start with t.areaname = '中国'
connect by t.parentareaid = prior t.areaid;
listagg：11gr2还新增了一个分析函数LISTAGG，这个函数的功能实现字符串的连接
create table t (id number, name varchar2(30), type varchar2(20));
insert into t
select rownum, object_name, object_type from dba_objects;
select listagg(name, ',') within group(order by id)
from t
where rownum < 10;
select type, listagg(name, ',') within group(order by id) name
from t
where type in ('DIRECTORY', 'JAVA SOURCE', 'SCHEDULE')
group by type;
select name,
listagg(name, ',') within group(order by id) over(partition by type) s_name
from t
where type in ('DIRECTORY', 'JAVA SOURCE', 'SCHEDULE');