ORACLE中的LISTAGG

Question

I am trying to use LISTAGG() to fetch more than two columns.

SELECT deptname, deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees 
FROM emp 
GROUP BY deptno;

But it is throwing this error:

: FROM keyword not found where expected
 00000 -  "FROM keyword not found where expected"
*Cause:    
*Action:
Error at Line: 3 Column: 12

Can please somebody explain why it is?

Answer 1

The LISTAGG analytic function was introduced in Oracle 11g Release 2 . So, if you are on older version, you won't be able to use it.

The error seems strange. You should actually get ORA-00904: "DEPTNAME": invalid identifier as the standard EMP table in SCOTT schema doesn't have DEPTNAME column. Also, you should get ORA-00979: not a GROUP BY expression as you did not mention the SELECT ed columns in the GROUP BY expression.

Using the standard EMP table in SCOTT schema:

SQL> SELECT deptno,
  2    job,
  3    LISTAGG(ename, ',') WITHIN GROUP (
  4  ORDER BY ename) AS employees
  5  FROM emp
  6  GROUP BY deptno,
  7    job;

    DEPTNO JOB       EMPLOYEES
---------- --------- ------------------------
        10 CLERK     MILLER
        10 MANAGER   CLARK
        10 PRESIDENT KING
        20 CLERK     ADAMS,SMITH
        20 ANALYST   FORD,SCOTT
        20 MANAGER   JONES
        30 CLERK     JAMES
        30 MANAGER   BLAKE
        30 SALESMAN  ALLEN,MARTIN,TURNER,WARD

9 rows selected.

SQL>

Answer 2

Try:

SELECT deptname, deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees 
FROM emp 
GROUP BY deptno,deptname;

Answer 3

Oracle 11g:

SELECT deptname, deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY deptno,job) AS employees 
FROM emp 
GROUP BY deptno,job;

Oracle 10g:

SELECT deptname, deptno, WMSYS.WM_CONCAT(ename) AS employees 
FROM emp 
GROUP BY deptno,job;