title: Replacing a table if another table exists
body: <p>I have 2 MySQL tables:</p>
  <ol>
  <li>'table_a'</li>
  <li>'table_b' which contains updated content of 'table_a'.</li>
  </ol>
  <p>I want 'table_b' to replace 'table_a' and be called 'table_a', but only if 'table_b' exists. Otherwise, do nothing.</p>
  <p>I have tried using a combination of <code>DROP TABLE IF EXISTS table_a</code> and <code>RENAME TABLE table_b TO table_a</code> without any success.</p>
  <p>Is this the correct approach?</p>