Oracle11.2新增了LISTAGG函数，可以用于字符串聚集，测试如下：

1,版本
SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

2，测试数据
SQL>
SQL> select empno,ename,deptno from scott.emp;

EMPNO ENAME      DEPTNO
----- ---------- ------
7369 SMITH          20
7499 ALLEN          30
7521 WARD           30
7566 JONES          20
7654 MARTIN         30
7698 BLAKE          30
7782 CLARK          10
7788 SCOTT          20
7839 KING           10
7844 TURNER         30
7876 ADAMS          20
7900 JAMES          30
7902 FORD           20
7934 MILLER         10

14 rows selected

3，作为聚集函数
SQL> SELECT deptno,
2         LISTAGG(ename, ',') WITHIN GROUP(ORDER BY ename) AS employees
3    FROM scott.emp
4   GROUP BY deptno;

DEPTNO EMPLOYEES
------ --------------------------------------------------------------------------------
    10 CLARK,KING,MILLER
    20 ADAMS,FORD,JONES,SCOTT,SMITH
    30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD

SQL>
--更换排序列
SQL> SELECT deptno,
2         LISTAGG(ename, ',') WITHIN GROUP(ORDER BY hiredate) AS employees
3    FROM scott.emp
4   GROUP BY deptno;

DEPTNO EMPLOYEES
------ --------------------------------------------------------------------------------
    10 CLARK,KING,MILLER
    20 SMITH,JONES,FORD,SCOTT,ADAMS
    30 ALLEN,WARD,BLAKE,TURNER,MARTIN,JAMES

--order by必须存在
SQL> SELECT deptno,
2         LISTAGG(ename, ',') WITHIN GROUP() AS employees
3    FROM scott.emp
4   GROUP BY deptno;

SELECT deptno,
       LISTAGG(ename, ',') WITHIN GROUP() AS employees
FROM scott.emp
GROUP BY deptno

ORA-30491: ORDER BY 子句缺失

SQL> SELECT deptno,
2         LISTAGG(ename, ',') WITHIN GROUP(order by null) AS employees
3    FROM scott.emp
4   GROUP BY deptno;

DEPTNO EMPLOYEES
------ --------------------------------------------------------------------------------
    10 CLARK,KING,MILLER
    20 ADAMS,FORD,JONES,SCOTT,SMITH
    30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
==〉按字母顺序排列

4，LISTAGG作为分析函数使用
SQL> SELECT empno,
2         ename,
3         deptno,
4         LISTAGG(ename, ',') WITHIN GROUP(ORDER BY ename) over(partition by deptno) AS employees
5    FROM scott.emp;

EMPNO ENAME      DEPTNO EMPLOYEES
----- ---------- ------ --------------------------------------------------------------------------------
7782 CLARK          10 CLARK,KING,MILLER
7839 KING           10 CLARK,KING,MILLER
7934 MILLER         10 CLARK,KING,MILLER
7876 ADAMS          20 ADAMS,FORD,JONES,SCOTT,SMITH
7902 FORD           20 ADAMS,FORD,JONES,SCOTT,SMITH
7566 JONES          20 ADAMS,FORD,JONES,SCOTT,SMITH
7788 SCOTT          20 ADAMS,FORD,JONES,SCOTT,SMITH
7369 SMITH          20 ADAMS,FORD,JONES,SCOTT,SMITH
7499 ALLEN          30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
7698 BLAKE          30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
7900 JAMES          30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
7654 MARTIN         30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
7844 TURNER         30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
7521 WARD           30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD

14 rows selected

5,其他实现方法参考
--model
SQL> SELECT deptno, vals
2    FROM (SELECT deptno, RTRIM(vals, ',') AS vals, rn
3            FROM scott.emp MODEL PARTITION BY(deptno) DIMENSION BY(ROW_NUMBER() OVER(PARTITION BY deptno ORDER BY ename) AS rn) MEASURES(CAST(ename AS VARCHAR2(4000)) AS vals) RULES(vals [ ANY ] ORDER BY rn DESC = vals [ CV() ] || ',' || vals [ CV() + 1 ]))
4   WHERE rn = 1
5   ORDER BY deptno;

    DEPTNO VALS
---------- --------------------------------------------------------------------------------
        10 CLARK,KING,MILLER
        20 ADAMS,FORD,JONES,SCOTT,SMITH
        30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD

--表函数：WMSYS.WM_CONCAT，10G已经提供该函数
SQL>
SQL> SELECT deptno, WMSYS.WM_CONCAT(ename) AS vals --<-- WM_CONCAT ~= STRAGG
2    FROM scott.emp
3   GROUP BY deptno;

DEPTNO VALS
------ --------------------------------------------------------------------------------
    10 CLARK,MILLER,KING
    20 SMITH,FORD,ADAMS,SCOTT,JONES
    30 ALLEN,JAMES,TURNER,BLAKE,MARTIN,WARD

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Oracle11.2新特性之listagg函数

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