Oracle按分组拼串逗号间隔

  select pe_no,advice_groupno,advice_code,advice_class,bg_flagchar,WMSYS.WM_CONCAT(ITEM_CODE)
  from(
  SELECT a.PE_NO, 
         a.ADVICE_GROUPNO,            
         a.advice_code,
a.advice_class,
         b.BG_FLAGCHAR,
         b.item_code
    FROM CPW_CODE_ADVICE a,CPW_CODE_ADVICE_ENTRY b  
   WHERE ( a.CPW_VER = b.CPW_VER ) and  
         ( a.CPW_CODE = b.CPW_CODE ) and  
         ( a.PE_NO = b.PE_NO ) and  
         ( a.ADVICE_CODE = b.ADVICE_CODE ) and  
         ( ( a.GROUP_SELECT_TYPE = '1' ) OR  
         ( a.GROUP_SELECT_TYPE = '2' ))  AND  
         ( a.CPW_VER = :n_cpw_ver ) AND  
         ( a.CPW_CODE = :s_cpw_code ) AND  
         ( a.PE_NO <= :n_pe_no ) and
( a.advice_class <> '11' and a.advice_class <> '12' )
        order by a.ADVICE_GROUPNO,a.ADVICE_ROWNO,b.BG_FLAGCHAR,b.item_code
        )
        group by pe_no,advice_groupno,advice_code,advice_class,bg_flagchar