How to use GROUP BY on a CLOB column with Oracle?

Try this:

SELECT A.T_ID, B.T, MAX(A.V) 
FROM bdd.LOG A, bdd.T_B B
WHERE B.T_ID = A.T_ID
GROUP BY A.T_ID, B.T
HAVING MAX(A.V) < 1;

I'm very familiar with the phenomenon of writing queries for a table designed by someone else to do something almost completely different from what you want. When I've had this same problem, I've used.

GROUP BY TO_CHAR(theclob)

and then of course you have to TO_CHAR the clob in your outputs too.

Note that there are 2 levels of this problem... the first is that you have a clob column that didn't need to be a clob; it only holds some smallish strings that would fit in a VARCHAR2. My workaround applies to this.

The second level is you actually want to group by a column that contains large strings. In that case the TO_CHAR probably won't help.