Oracle11.2新特性之listagg函数(多条数据用逗号隔开)

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,LISTAGG(ename, ',') WITHIN GROUP(ORDER BY ename) AS employees
     FROM scott.emp 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,LISTAGG(ename, ',') WITHIN GROUP(ORDER BY hiredate) AS employees
      FROM scott.emp 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,LISTAGG(ename, ',') WITHIN GROUP() AS employees
      FROM scott.emp 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,LISTAGG(ename, ',') WITHIN GROUP(order by null) AS employees
      FROM scott.emp 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,ename,deptno,
      LISTAGG(ename, ',') WITHIN GROUP(ORDER BY ename) over(partition by deptno) AS employees
      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
      FROM (SELECT deptno, RTRIM(vals, ',') AS vals, rn
              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 ]))
     WHERE rn = 1 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(不好使)
SQL>
SQL> SELECT deptno, WMSYS.WM_CONCAT(ename) AS vals --<-- WM_CONCAT ~= STRAGG
    FROM scott.emp GROUP BY deptno;
 
DEPTNO VALS
------ --------------------------------------------------------------------------------
    10 CLARK,MILLER,KING
    20 SMITH,FORD,ADAMS,SCOTT,JONES
    30 ALLEN,JAMES,TURNER,BLAKE,MARTIN,WARD