oracle--合并行数据(拼接字符串)，获取查询数据的前3条数据...

--标准函数Lpad 可以实现左补零，但是如果多于需要长度，则会截断字符串
SELECT LPAD ('1' , 3 , '0') FROM DUAL -- return 001

情况一：需要补零。
    SELECT LPAD ('1' , 3 , '0') FROM DUAL
    结果：001 正确
情况二：不需要补零。
    SELECT LPAD ('001' , 3 , '0') FROM DUAL
    结果：001 错误

select 
  to_char(wmsys.wm_concat(
   queuesign
   ||(select LPAD(sortno,3,0)from dual)
   ||'('||
   patname||')'
    )) as WaitPatients
  from
        (--查询分组数据的前 3 条数据
            SELECT *        
               FROM (SELECT ROW_NUMBER() OVER(PARTITION BY cc.queuename ORDER BY cc.enroldate) rn,        
                     cc.*        
                     FROM
                     (      --查询已登记数据，根据队列、登记日期、状态排序--结束至bb
                               select * from
                                (select a.patname,a.queuesign,a.queuename,a.sortno,a.enroldate,a.status
                                from qs_register a where a.status='已登记'
                                group by a.patname,a.queuesign,a.queuename,a.sortno,a.enroldate,a.status
                                order by a.queuename,a.enroldate,a.status
                                ) bb
            )cc ) WHERE rn in(1,2,3)
) b
group by queuename

实例二

create or replace view VIEW_GETCALLANDWAITPATIENT as
select  *
--ok.queuename,ok.patname,ok.queuesign,ok.sortno,ok.enroldate,ok.status,ok.checkroom,ok.areapart,ok.ofdepart,ok.WaitPatients 
from
(
 SELECT ROW_NUMBER() OVER(PARTITION BY ok.queuename ORDER BY ok.enroldate) ook,        
                                 ok.*     
from (select * from
(
                SELECT *        
                   FROM (
                           SELECT ROW_NUMBER() OVER(PARTITION BY cc.queuename ORDER BY cc.enroldate) rn,        
                                 cc.*        
                                 FROM
                                             (select * from
                                                (select a.patname,a.queuesign,a.queuename,a.sortno,a.status,a.checkroom,a.areapart,a.enroldate,a.ofdepart
                                                from qs_register a where a.status='就诊中'
                                                group by a.patname,a.queuesign,a.queuename,a.sortno,a.status,a.checkroom,a.areapart,a.enroldate,a.ofdepart
                                                order by a.queuename,a.status,a.enroldate) bb)cc
                         )        
                  WHERE rn = 1
 ) mm,
 
--查询已登记每组前3条数据并合并为(1003(张三丰),1003(张三丰),1003(张三丰))
   (select 
            to_char(wmsys.wm_concat(
             queuesign
             ||(select LPAD(sortno,3,0)from dual)
             ||'('||
             patname||')'
              )) as WaitPatients
            from
                  (--查询分组数据的前 3 条数据
                      SELECT *        
                         FROM (SELECT ROW_NUMBER() OVER(PARTITION BY cc.queuename ORDER BY cc.enroldate) rn,        
                               cc.*        
                               FROM
                               (      --查询已登记数据，根据队列、登记日期、状态排序--结束至bb
                                         select * from
                                          (select a.patname,a.queuesign,a.queuename,a.sortno,a.enroldate,a.status,a.ofdepart
                                          from qs_register a where a.status='已登记'
                                          group by a.patname,a.queuesign,a.queuename,a.sortno,a.enroldate,a.status,a.ofdepart
                                          order by a.queuename,a.enroldate,a.status,a.ofdepart
                                          ) bb
                      )cc ) WHERE rn in(1,2,3)
          ) b
          group by queuename
)nn) ok  )
  WHERE ook = 1
 
--group by ok.queuename,ok.patname,ok.queuesign,ok.sortno,ok.enroldate,ok.status,ok.checkroom,ok.areapart,ok.ofdepart,ok.WaitPatients
   