title: Oracle : Automatic modification date on update
body: <p>i have a table in oracle and i want to study the updates on lines</p>
  
  <pre><code>id number,
  title varchar2(10),
  modify_date date
  </code></pre>
  
  <p>i have created a trigger to feed the modify_date :</p>
  
  <pre><code>create or replace
  TRIGGER schema.name_of_trigger
  BEFORE UPDATE ON schema.name_of_table
  FOR EACH ROW
  BEGIN
      :new.modify_date := sysdate;
  END;
  </code></pre>
  
  <p>but when i make a big update from another table i would like the modify_date to be updated ONLY for lines with a new value, not all lines.</p>
  
  <pre><code>update mytable a set title = (select title from mytable2 b where b.id = a.id)
  </code></pre>
  
  <p>Is it possible ? i thought Oracle would not update a field with the same value</p>
  
  <p>Thanks</p>