title: How to extract text before several specified alphanumeric whole words from string in plsql
body: <p>How to remove all characters after specific alphanumeric value from string
  for example &quot;covid19 1st case&quot; should be &quot;covid19&quot; if we remove string after 1st;
  in case of &quot;covid19 2d case&quot; it should be &quot;covid19&quot; if we remove string after 2d
  I am trying below query</p>
  <pre><code>select regexp_substr('covid19 1st case','[^1st]*') from dual;
  </code></pre>
  <p>but its giving covid as output any lead.
  if we have predefine alphanumeric values can we do it in single expression
  like we can remove all string after 1st and 2d.</p>
  <p>Thanks</p>