参考网址：

http://stackoverflow.com/questions/11541383/ordering-by-list-of-strings-in-oracle-sql-without-listagg

字符串拼接技巧和方式： http://www.oracle-base.com/articles/misc/string-aggregation-techniques.php

http://www.williamrobertson.net/documents/one-row.html

在进行使用WM_CONCAT或者自定义的聚合函数，进行拼串的时候，可能遇到拼串形成的结果集大于4000，这时候，系统会提示，超过系统限制。所以，在这个时候，最好的处理办法就是将结果集处理成CLOB格式，

下面共有两种处理方式：

1、使用函数

1 create or replace type str2tblType as table of varchar2(4000)
CREATE OR REPLACE FUNCTION tab2clob(p_str2tbltype str2tbltype,
                    p_delim       IN VARCHAR2 DEFAULT ',') RETURN CLOB IS
    l_result CLOB;
  BEGIN
    FOR cc IN (SELECT column_value
                 FROM TABLE(p_str2tbltype)
                ORDER BY column_value) LOOP
      l_result := l_result || p_delim || cc.column_value;
    END LOOP;
    RETURN ltrim(l_result, p_delim);
初始化数据：
1 BEGIN2   FOR idx IN 1 .. 10000 LOOP
3     INSERT INTO ts1 (tm) VALUES (sys_guid());
4   END LOOP;
5 END;
测试的SQL语句：
1 SELECT tab2clob(CAST(COLLECT(tm) AS str2tbltype)) attributes
2   FROM ts1
3  WHERE rownum < 1000
如下的SQL语句错误：由于类型不同
1 SELECT sys_util.tab2clob(CAST(COLLECT(deptno) AS str2tbltype))
2   FROM (SELECT DISTINCT deptno FROM emp)
会抛出如下的异常信息：
因为在str2tbltype中声明的是varchar2，但是现在deptno是数字，所以数据类型会发生不一致，所以，可以使用to_char见其进行转换，来避免上述的错误：
1 SELECT sys_util.tab2clob(CAST(COLLECT(to_char(deptno)) AS str2tbltype))
2   FROM (SELECT DISTINCT deptno FROM emp)
 二：使用Oracle的SQL提供的处理XML的语句：XMLAGG()
SQL语句如下：
1 SELECT rtrim(xmlagg(xmlparse(content ename || ',' wellformed) ORDER BY ename)
2              .getclobval(),
3              ',') attributes,
4        deptno
5   FROM emp
6  GROUP BY deptno;
1  SELECT deptno,
2        trim(xmlagg(xmlelement(content, ename || ',' ) ORDER BY ename)
3              .extract('//text()').getclobval())
4               AS concatenated
5   FROM emp
6  GROUP BY deptno;
下面的语句，没有调用getClobVal（），聚合的结果集是字符串
1  SELECT deptno,
2        trim(xmlagg(xmlelement(content, ename || ',' ) ORDER BY ename)
3              .extract('//text()'))
4               AS concatenated
5   FROM emp
6  GROUP BY deptno;
关于Oracle中XML的知识，请参考：http://www.oratechinfo.co.uk/sqlxml.html
WMSYS.WM_CONCAT使用方法如下：
SELECT CUST_NO,
                       SUM(AC.MONEY) AS MONEY,
                       SUM(AC.INVOPRINT) AS INVOPRINT,
                       MIN(AC.STARTTIME) AS STARTTIME,
                       MAX(AC.ENDTIME) AS ENDTIME,
                       WMSYS.WM_CONCAT(AC.ACCOUNTNO) ACCOUNTNO
                  FROM T_ACCOUNT AC,
                       T_FEETYPE FEE,
                       --T_SUBMITDETAILTOACCOUNT S,
                       (SELECT ACCOUNTNO, ACCTYPEID
                          FROM T_ACCUSTACCBOOKDETAIL
                         GROUP BY ACCOUNTNO, ACCTYPEID) D
                 WHERE AC.FEECODE = FEE.FEECODE
                      --AND AC.ACCOUNTNO = S.ACCOUNTNO
                   AND AC.ACCOUNTNO = D.ACCOUNTNO
                   AND D.ACCTYPEID = '0001'
                   AND AC.ACCSTATUS = '4'
                   AND AC.INVOPRINT = 0
                   AND FEE.FEETYPE_TYPE = :feeType
                      --AND S.FLAG = '1'
                   AND AC.PAYDATE >= TO_DATE(:startdate, 'YYYY-MM-DD')
                   AND AC.PAYDATE < TO_DATE(:enddate, 'YYYY-MM-DD') + 1
                 GROUP BY CUST_NO