ALTER TABLE statement causes generating strange UPDATE statement

Hi,

i have table PARTICIPANTS with column UPLOADED_ID_PARTICIPANTS_FLAG CHAR(1) NOT NULL. When i try to modify that column to NULL by using

ALTER TABLE PARTICIPANTS MODIFY UPLOADED_ID_PARTICIPANTS_FLAG NULL;

then Oracle generates this update statement (but only on some instances):

UPDATE PARTICIPANTS set UPLOADED_ID_PARTICIPANTS_FLAG = UPLOADED_ID_PARTICIPANTS_FLAG;

This statement causes problem because there is a trigger on table, which fires exception.

Does anybody know why Oracle generates that statement?

Thanks,

R. Kazimir

robert.kazimir@rb.cz