ORACLE中的LISTAGG

Question

我正在尝试使用LISTAGG()来获取两个以上的列。

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

但是它抛出了这个错误：

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

有人能解释一下为什么会这样吗？

Answer 1

Oracle分析函数是在Oracle11g Release 2中引入的。因此，如果你使用的是旧版本，你将无法使用它。

这个错误看起来很奇怪。您实际上应该获取ORA-00904: "DEPTNAME": invalid identifier，因为SCOTT模式中的标准EMP表没有DEPTNAME列。此外，您应该得到ORA-00979: not a GROUP BY expression，因为您没有在GROUP BY表达式中提到SELECTed列。

使用SCOTT模式中的标准EMP表：

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

尝试：

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

Answer 3

Oracle11g：

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

Oracle10g：

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