①聚合函数，当然也可以用自定义函数实现，主要是利用了GROUP BY和聚合函数分组。
修改前：
select distinct sn.s_num, con1.flag con_flag, con1.id con_id, con1.name con_name, con1.mobile con_mobile, con2.flag con2_flag, con2.id con2_id, con2.name con2_name, con2.mobile con2_mobile, s.id s_id, s.name stu_name
from table_snumber sn, table_c con1, table_c con2, table_s s
where sn.stu_id(+)=s.id
and con2.r_no(+)=2
and con2.s_id(+)=s.id
and con1.r_no(+)=1
and con1.s_id(+)=s.id
and s.u_id=:1
order by sn.s_num, s.name
修改后：
SELECT SN.S_NUM,
MAX(DECODE(C.R_NO,1,C.FLAG,NULL)),
MAX(DECODE(C.R_NO,1,C.ID,NULL)),
MAX(DECODE(C.R_NO,1,C.NAME,NULL)),
MAX(DECODE(C.R_NO,1,C.MOBILE,NULL)),
MAX(DECODE(C.R_NO,2,C.FLAG,NULL)),
MAX(DECODE(C.R_NO,2,C.ID,NULL)),
MAX(DECODE(C.R_NO,2,C.NAME,NULL)),
MAX(DECODE(C.R_NO,2,C.MOBILE,NULL)),S.ID S_ID,S.NAME STU_NAME
FROM STU_NUMBER SN, CONNECTOR C, STUDENT S
WHERE SN.S_ID(+)=S.ID
AND C.S_ID(+)=S.ID
AND S.UNIT_ID=665543--:1
GROUP BY SN.S_NUM,S.ID,S.NAME
ORDER BY SN.S_NUM, S.NAME
-----少关联了TABLE_C和少了一个distinct。
②使用wm_sys.wm_concat
select *
from dba_source d
where d.type='FUNCTION'
and d.name='WM_CONCAT'
-----已经加密过 那么怎么用？咕狗或者用PL/SQL看一下。
select wmsys.wm_concat(c.MOBILE),wmsys.wm_concat(c.NAME),wmsys.wm_concat(c.id)
from TABLE_C C
where c.U_ID=665543
group by c.S_ID（还有个order
by选项）
-------输出格式为
13500000000,1590000000 张之夏,庄之俊 5941820,5941821
与要求格式不太相符 也是可以处理的 还是选择聚合函数
③使用sys_connect_by_path
不再测试。
详见：
http://www.ningoo.net/html/2008/how_to_do_string_aggregate_on_oracle.html
