title: Nullify an inserting value in a row trigger
body: <p>I have a problem with my database trigger in which I'm supposed to nullify the inserted/updated value (<code>RESULTATOBT</code>), although I need the OLD/NEW variables, so I can't apply <a href="https://stackoverflow.com/questions/29799454/insert-trigger-subtracting-values">this solution (updating the table in the table trigger)</a>.</p>
  
  <p>The error is a mutating table one; due to modifying a table in a <em>for each row</em> trigger.</p>
  
  <p>Here's the concerned extract of my code:</p>
  
  <pre><code>CREATE OR REPLACE TRIGGER VERIF_RESULTATS
    AFTER INSERT OR UPDATE OF RESULTATOBT
    ON PARTICIPATION
    FOR EACH ROW
    FOLLOWS VERIF_PARTICIPATION
    WHEN ( NEW.RESULTATOBT IS NOT NULL )
  BEGIN 
    UPDATE PARTICIPATION p
    SET RESULTATOBT = NULL
    WHERE p.CDPERS = :NEW.CDPERS
      AND p.CDCOMPET = :NEW.CDCOMPET;
  END;
  /
  </code></pre>
  
  <p>Thank you in advance for your help.</p>
  
  <p>N.B.: I'm a relatively new member, so I might require additional advices/edits if my question doesn't fit the proper format.</p>