title: Adding a row to a resultset if it does not exist using Oracle Model Clause
body: <p>Given the table</p>
  <pre><code>D           V
  --------------
  2019-03-02, 13
  2019-10-28, 12
  2019-11-22, 34
  2020-01-18, 21
  2020-04-11, 39
  </code></pre>
  <p>I want to add a record with date 2019-12-31 replicating the last one partitioning by year</p>
  <pre><code>2019-03-02, 13
  2019-10-28, 12
  2019-11-22, 34
  2019-12-31, 34 &lt;&lt;
  2020-01-18, 21
  2020-04-11, 39
  2020-12-31, 39 &lt;&lt;
  </code></pre>
  <p>How can this be made using the Model Clause? I cannot even figure out where to start.</p>