select chgdetail_id,
       chgdetail_custname
       min(decode(seq, 1, serv_devcode, NULL)) || ',' ||
       min(decode(seq, 2, serv_devcode, NULL)) || ',' ||
       min(decode(seq, 3, serv_devcode, NULL))
       chgdetail_roperatorid
  from (select chgdetail_id,
               chgdetail_custname,
               serv_devcode,
               row_number() over(partition by chgdetail_id order by chgdetail_id asc) seq
          from (select c.id chgdetail_id,
                       c.custname chgdetail_custname,
                       serv.devcode serv_devcode
                  from chgdetail c
                  left outer join serv serv on c.racctid = serv.racctid
                 where
                 group by c.id,
                          c.custname,
                          serv.devcode))
 where seq < 4
 group by chgdetail_id,
     chgdetail_custname
SQL说明：当查询出结果的相连的数量(如上SQL只要求电话号前三位通过“，”相连)有限制或相同需求时，可用decode相连。

---------------------------------------------------------------------------------------------------------------------------------
说人之短，乃护己之短。夸己之长，乃忌人之长。皆由存心不厚，识量太狭耳。能去此弊，可以进德，可以远怨。
http://www.blogjava.net/szhswl
------------------------------------------------------------------------------------------------------ ----------------- ---------