title: Oracle regex expression sorting out special characters and Czech characters
body: <p>Due to a interface with a bank I need to sort out some unwanted characters from a name field: </p>
  
  <p>This is the permitted range:
  0 - 9, a - z, A - Z, / - ? ( ) . , ' + (space) – but no Czech characters allowed</p>
  
  <p>I've tried something like this getting unwanted hits on several period . and spaces, but not getting there 100%:</p>
  
  <pre><code>SELECT CASE
            WHEN  REGEXP_LIKE (name,
                              '^([0-9a-zA-Z]* *+(|_|\-|\.))')
            THEN
               'true'
            ELSE
               'false'
         END AS tmp, avt.*
    FROM amcbankvendtable avt
  </code></pre>
  
  <p>In addition I still havent removed czech characters. I know that the parameter character class <code>==a==</code> gives <code>ä</code> , but in this case I want the opposite, not allow <code>ûü</code>, but only <code>u</code>. (Basically only allow the english alpabeth).</p>
  
  <p>So: </p>
  
  <ul>
  <li><p>123456abc is okay</p></li>
  <li><p>123û  is not okay</p></li>
  <li><p>123#&amp; is not okay (#&amp; not allowed characters)</p></li>
  </ul>
  
  <p>Any ideas?</p>