LISTAGG与WMSYS.WM_CONCAT的简单用法

TheLISTAGGanalytic function was introduced in Oracle 11g Release 2, making it very easy to aggregate strings. The nice thing about this function is it also allows us to order the elements in the concatenated list.

Base Data:

    DEPTNO ENAME
---------- ----------
        20 SMITH
        30 ALLEN
        30 WARD
        20 JONES
        30 MARTIN
        30 BLAKE
        10 CLARK
        20 SCOTT
        10 KING
        30 TURNER
        20 ADAMS
        30 JAMES
        20 FORD
        10 MILLER
SELECT deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees
FROM   emp
GROUP BY deptno;
Desired Output:

    DEPTNO EMPLOYEES
---------- --------------------------------------------------
        10 CLARK,KING,MILLER
        20 SMITH,FORD,ADAMS,SCOTT,JONES
        30 ALLEN,BLAKE,MARTIN,TURNER,JAMES,WARD
You can also use functionWMSYS.WM_CONCAT()
for example:
select id,val from idtable;

ID VAL
---------- --------------------
10 abc
10 abc
10 def
10 def
20 ghi
20 jkl
20 mno
20 mno

8 rows selected

SQL> commit;

Commit complete

SQL>
SQL> SELECT ID,WMSYS.WM_CONCAT(VAL)AS ENAMES
2 FROM IDTABLE
3 GROUP BY ID;

ID ENAMES
---------- --------------------------------------------------------------------------------
10 abc,abc,def,def
20 ghi,jkl,mno,mno