ORA-12704: character set mismatch问题、以及处理wm_concat函数clob乱码问题

<pre name="code" class="html">

在utf8数据库里编译存储过程，遇到这个问题.
oracle9206
sql: [做了简化]
select a from t1
union all
select '1' from t2;
其中t1.a是nvarchar2类型。

解决办法很简单:
select a from t1
union all
select N'1' from t2;

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select em.devicename,
to_char(em.faulttime, 'yyyy-mm-dd hh24:mi:ss') faulttime,
et.enumname maintainstatus,
(case
when (em.DPLANREPAIRTIME >= em.drealrepairtime) or
(sysdate < em.dplanrepairtime) then
'及时'
when (em.dplanrepairtime < em.drealrepairtime) or
(em.drealrepairtime is null and em.dplanrepairtime < sysdate) then
'不及时'
when (em.dplanrepairtime is null and em.drealrepairtime is null and
(em.faulttime + esl.finishtime / 24) > sysdate) then
'及时'
when (em.dplanrepairtime is null and em.drealrepairtime is null and
(em.faulttime + esl.finishtime / 24) < sysdate) then
'不及时'
end) overdue,
et1.enumname faultfrom,
em.CBUGDETAIL,
to_char((select wm_concat(to_char(eti.track_time,
'yyyy-mm-dd hh24:mi:ss') || ' ' ||
eti.track_info || '【' || eti.track_man || '】')
from equip_maintain_tracking_info eti
where eti.maintain_id = em.maintainid)) genjin,
et2.enumname resultstatus, to_char(em.drealrepairtime, 'yyyy-mm-dd hh24:mi:ss') nworkhour,
(case
when sps.connection_name is null then
''
else
sps.connection_name || '-' || sps.connection_phone
end) crepairid,
et3.enumname faulttype
from equip_maintain em
left join enum_type et
on et.enumvalue = em.maintain_status
and et.enumtypeid = '75'
left join enum_type et1
on et1.enumvalue = em.fault_from
and et1.enumtypeid = '74'
left join enum_type et2
on et2.enumvalue = em.result_status
and et2.enumtypeid = '76'
left join equip_service_level esl
on esl.name = em.service_level
left join Equip_Service_Provider_Sms sps
on sps.id = em.crepairid
left join enum_type et3
on em.fault_type = et3.enumvalue
and et3.enumtypeid = '77'
where em.cequipid = '370200000000080004'
and (em.result_status = 1 or em.result_status is null)
and em.faulttime >= to_date('20151127', 'yyyymmdd')
and em.faulttime <= to_date('20151226235959', 'yyyymmddhh24miss')
order by em.faulttime desc