title: Make 2 tables identical on every form submission
body: <p>I have 2 tables (with identical structure) and I want both to update after a form submission and both have the exact same data.</p>
  
  <p>The tables structure are as below:</p>
  
  <p>id | parent_id | name | surname</p>
  
  <p>The <code>id</code> is the primary key, which means that I cannot execute the following query because it throws an error (Duplicate entry '1' for key 'PRIMARY'):</p>
  
  <p><code>INSERT INTO table_2 SELECT * FROM table_1</code></p>
  
  <p>My goal is to keep the data identical (including the <code>PRIMARY</code>) in both tables after a <strong>row is updated</strong> or a <strong>new row is added</strong>. How can I do this and avoid the <em>Duplicate entry</em> error?</p>