title: mySQL Select priority - select one row OR another (select a default or "fallback" row)
body: <p>This should be fairly simple but it's tricky to find the right term to use when searching.</p>
  
  <p>In the query below, I need to select <code>WHERE lang='en'</code> ONLY if <code>WHERE lang='nl_NL'</code> returns nothing. In other words, I want to find all records <code>WHERE script='generic'</code>, prioritised by <code>lang=nl_NL</code></p>
  
  <pre><code>SELECT * FROM international WHERE script='generic' AND (lang = 'nl_NL' OR lang = 'en')
  </code></pre>