wmsys.wm_concat结果长度限制的问题

转：http://bbs.csdn.net/topics/360059765

使用wmsys.wm_concat多列合成一列遇到问题
ORA-22813: 操作数值超出系统的限制

官方文档解释是总长度超过30k
有办法修改这个长度限制么？

已经写了存储过程作为替代方案了

CREATE OR REPLACE TYPE zh_concat_im
AUTHID CURRENT_USER AS OBJECT
(
  CURR_STR clob,
  STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im) RETURN NUMBER,
  MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,
  P1 IN VARCHAR2) RETURN NUMBER,
  MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN zh_concat_im,
  RETURNVALUE OUT clob,
  FLAGS IN NUMBER)
  RETURN NUMBER,
  MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT zh_concat_im,
  SCTX2 IN zh_concat_im) RETURN NUMBER
);

CREATE OR REPLACE TYPE BODY zh_concat_im
IS
  STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im)
  RETURN NUMBER
  IS
  BEGIN
  SCTX := zh_concat_im(NULL) ;
  RETURN ODCICONST.SUCCESS;
  END;
  MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,

  P1 IN VARCHAR2)
  RETURN NUMBER
  IS
  BEGIN
  IF(CURR_STR IS NOT NULL) THEN
  CURR_STR := CURR_STR || ',' || P1;
  ELSE
  CURR_STR := P1;
  END IF;
  RETURN ODCICONST.SUCCESS;
  END;
  MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN zh_concat_im,
  RETURNVALUE OUT clob,
  FLAGS IN NUMBER)
  RETURN NUMBER
  IS
  BEGIN
  RETURNVALUE := CURR_STR ;
  RETURN ODCICONST.SUCCESS;
  END;
  MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT zh_concat_im,
  SCTX2 IN zh_concat_im)
  RETURN NUMBER
  IS
  BEGIN
  IF(SCTX2.CURR_STR IS NOT NULL) THEN
  SELF.CURR_STR := SELF.CURR_STR || ',' || SCTX2.CURR_STR ;
  END IF;
  RETURN ODCICONST.SUCCESS;
  END;
END;

create or replace FUNCTION zh_concat(P1 VARCHAR2)
RETURN clob AGGREGATE USING zh_concat_im ;