using DBMS_LOB.COMPARE on clobs in a trigger to compare old vs new
I am working on an after-update trigger that will compare the old and new values of a clob column. The triggering statement would be "update mytable set CLOBCOL=my_updated_clob where thekey = primary-key-identifier". However, the standard old vs new nomencature in the trigger does not seem to work:
if (dbms_lob.compare(:new.CLOBCOL,:old.CLOBCOL) != 0) then ...
The compare returns a null value. I think it is because the :old.CLOBCOL is not open, so it has no lob locator reference. How can I compare the old value to the new value?
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