Help in using listagg function for more than 8000 char.

Question

Hi Friends,
Need you urgent help in using listagg function for more than 8000 char.
I did the below sample SQL and in "e_orig" and "d_orig" for upto 4000 char it is working fine but I have to use it for more than 8000 char. and it is giving error,
I checked the listagg function is having limitation of 4000 char.
I tried but I am unable to achive this. Can someone provide me a sample example to achive this
select d.dname,d.loc,e.hiredate
,listagg(e.ename,',' ) within group (order by e.deptno) over (partition by e.deptno) as e_orig
,listagg(e.ename, ',') within group (order by e.sal) over (partition by e.deptno) as d_orig
from emp e, dept d
where e.deptno=d.deptno;[ This is my first post, I gone through the guideline for posting a post , and try to go according to that ( I have not pasted here create table and insert as I have used basic table emp, dept for example), please let me know if still I should give this, I will take care from my next post ]
Thanks in advance

Answer 1

Interesting, I didn't know you could do that, but...
BluShadow wrote:
You could write some PL/SQL code that does it all for you, but that would involve loops and would be slow.Well, objects are written in PL/SQL aren't they? And presumably there'll be implicit looping too? So it's not at all obvious that this method will be faster than doing the joining in PL/SQL in memory. The only way to find out is to benchmark them - so I have done that.
I noticed that OP's ref cursor actually only ever retrieves a single record for a bound department number, so I decided the best thing would be to test using a procedure that passes an output string back. I selected all (109) employees and put spaces in to ensure above 4000 characters. I also noticed that as he is using PL/SQL he probably can use a VARCHAR2 type, but just not ListAgg in the query, so I wrote short procedures as follows:
SimpleAggChr     - bulk collect and array processing, VARCHAR2 output
ClobAggPrc     - the custom aggregation method, CLOB output
SimpleAggClob     - bulk collect and array processing, CLOB output
I then wrote a driving script that calls them in the order above and times each call (I like benchmarking so I have my own timing object to make it easy). I then print the lengths for checking, and my object writes the timings to my output table. Running a few times I got varying results, but generally it looks like there isn't a lot to choose between them for performance.
Here's the procedure code:
CREATE OR REPLACE TYPE char100_list_type AS TABLE OF VARCHAR2(100)
CREATE OR REPLACE PROCEDURE SimpleAggChr (x_out OUT VARCHAR2) IS
  l_enames     char100_list_type;
BEGIN
  SELECT first_name || '                                        ' || last_name
    BULK COLLECT INTO l_enames
    FROM employees
   ORDER BY salary;
  FOR i IN 1..l_enames.COUNT LOOP
    x_out := x_out || l_enames(i) || ',';
  END LOOP;
END SimpleAggChr;
CREATE OR REPLACE PROCEDURE SimpleAggClob (x_out OUT CLOB) IS
  l_enames     char100_list_type;
BEGIN
  SELECT first_name || '                                        ' || last_name
    BULK COLLECT INTO l_enames
    FROM employees
   ORDER BY salary;
  FOR i IN 1..l_enames.COUNT LOOP
    x_out := x_out || l_enames(i) || ',';
  END LOOP;
END SimpleAggClob;
SHO ERR
PROMPT ClobAggPrc
CREATE OR REPLACE PROCEDURE ClobAggPrc (x_out OUT CLOB) IS
BEGIN
  SELECT clobagg(first_name || '                                        ' || last_name || ',')
    INTO x_out
    FROM employees
   ORDER BY salary;
END ClobAggPrc;
SHO ERRand the driving script:
SET SERVEROUTPUT ON
SET TIMING ON
DECLARE
  l_enames_c1     CLOB;
  l_enames_c2     CLOB;
  l_enames_v     VARCHAR2(32767);
  l_timer     timer_set_type := timer_set_type ('Aggregation');
BEGIN
  Utils.g_id := 'Aggregation';
  SimpleAggChr (l_enames_v);
  l_timer.Increment_Time ('SimpleAggChr');
  ClobAggPrc (l_enames_c1);
  l_timer.Increment_Time ('ClobAggPrc');
  SimpleAggClob (l_enames_c2);
  l_timer.Increment_Time ('SimpleAggClob');
  DBMS_Output.Put_Line ('SimpleAggChr returned string of length ' || Length (l_enames_v));
  DBMS_Output.Put_Line ('ClobAggPrc returned string of length ' || Length (l_enames_c1));
  DBMS_Output.Put_Line ('SimpleAggClob returned string of length ' || Length (l_enames_c2));
  l_timer.Write_Times;
END;
SET TIMING OFF
SET LINES 150
SET PAGES 1000
COLUMN id FORMAT A30
COLUMN line_text FORMAT A120
SELECT line_text
  FROM output_log
WHERE id = 'Aggregation'
ORDER BY line_ind
/and the results:
SimpleAggChr returned string of length 5779
ClobAggPrc returned string of length 5779
SimpleAggClob returned string of length 5779
PL/SQL procedure successfully completed.
Elapsed: 00:00:27.05
LINE_TEXT
Timer Set: Aggregation, constructed at 03 Nov 2011 16:27:07, written at 16:27:35
================================================================================
[Timer timed: Elapsed (per call): 0.02 (0.000016), CPU (per call): 0.01 (0.000010), calls: 1000, '***' denotes corrected
line below]
Timer              Elapsed          CPU          Calls        Ela/Call        CPU/Call
SimpleAggChr          9.84         0.36              1         9.84400         0.36000
ClobAggPrc            9.37         0.32              1         9.37400         0.32000
SimpleAggClob         8.25         0.22              1         8.25000         0.22000
(Other)               0.00         0.00              1         0.00000         0.00000
Total                27.47         0.90              4         6.86700         0.22500
13 rows selected.