SELECT A CLOB - GROUP BY

Hi,

I am having trouble selecting a CLOB (CASE_LIST), here is what
happens:

SELECT PRODUCT_NAME AS "Product Name", SUM(CASES_CREATED) AS "Cases
Created",
CASE_LIST
FROM PEOPLESOFTBUCUSTPROD
GROUP BY PRODUCT_NAME, CASE_LIST
ORDER BY PRODUCT_NAME

I get this error: ORA-00932: inconsistent datatypes: expected - got
CLOB

Then I did this, using TO_CHAR:

SELECT PRODUCT_NAME AS "Product Name", SUM(CASES_CREATED) AS "Cases
Created",
TO_CHAR(CASE_LIST)
FROM PEOPLESOFTBUCUSTPROD
GROUP BY PRODUCT_NAME, TO_CHAR(CASE_LIST)
ORDER BY PRODUCT_NAME

I get this error: ORA-22835: Buffer too small for CLOB to CHAR or BLOB
to RAW conversion (actual: 4997, maximum: 4000)

So lastly I did this, using DBMS_LOB.SUBSTR:

SELECT PRODUCT_NAME AS "Product Name", SUM(CASES_CREATED) AS "Cases
Created",
DBMS_LOB.SUBSTR(CASE_LIST, 4000, 1) CASE_LIST
FROM PEOPLESOFTBUCUSTPROD
GROUP BY PRODUCT_NAME, DBMS_LOB.SUBSTR(CASE_LIST, 4000, 1)
ORDER BY PRODUCT_NAME

I am now able to get results, but my data is truncated at 4000
characters, which will not work

Any ideas on how to get the full clob results in one query?