title: ORA-25006 in a FOR UPDATE of CLOB column
body: <p>I'm attempting to avoid an update with a null value in a CLOB column (for other reasons the column can not have a NOT NULL constraint).</p>
  
  <p>I wrote this trigger:</p>
  
  <pre><code>create or replace TRIGGER "TEST_NULL"
  BEFORE UPDATE OR INSERT OF MY_CLOB_COLUMN
  ON T
  FOR EACH ROW
  begin
  
       if (:old.MY_CLOB_COLUMN is not null and :new.MY_CLOB_COLUMN is null) then
  
         RAISE_APPLICATION_ERROR(-20001, 'error');
  
       end if;  
  
  END;
  </code></pre>
  
  <p>However, I'm getting a </p>
  
  <blockquote>
    <p>ORA-25006: cannot specify this column in UPDATE OF clause.</p>
  </blockquote>
  
  <p>How can I solve this?</p>