title: regex: Find next or previous letter in the alphabet
body: <p>I have an Oracle SQl table with 2 colunms, value and positionid, value goes from -10 to 10 and positionid from A01 to K25.</p>
  <p>I need to find out which neighboring position have a difference higher or equal to 5. A neighbor position is determined by its positionid according with the alphabet and the number order, something like in the below table:, B02 will have as neighbor positions A01, A02, A03, B01, B03, C01, C02 and C03</p>
  <pre><code>| A01 | A02 | A03 | A04 |
  | B01 | B02 | B03 | B04 |
  | C01 | C02 | C03 | C04 |
  | D01 | D02 | D03 | D04 |
  </code></pre>
  <p>For example:</p>
  <ul>
  <li>Position B02 with value 5 and C03 with value -5 <strong>match</strong> that condition because they are neighbours and the value difference is higher than 5.</li>
  <li>Position B02 with value 5 and C03 with value 4 <strong>doesn`t match</strong> that condition because they are neighbours but the value difference is lower than 5.</li>
  <li>Position A20 with value 5 and E05 with value -5 <strong>doesn't match</strong> the condition because they are not neighbours.</li>
  </ul>
  <p>Any suggestion for the SQL query or at least a regex to find those neighbours positions?</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>value</th>
  <th>positionid</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>2</td>
  <td>A01</td>
  </tr>
  <tr>
  <td>-4</td>
  <td>A02</td>
  </tr>
  <tr>
  <td>7</td>
  <td>A03</td>
  </tr>
  <tr>
  <td>.</td>
  <td>.</td>
  </tr>
  <tr>
  <td>4</td>
  <td>C12</td>
  </tr>
  <tr>
  <td>2</td>
  <td>C13</td>
  </tr>
  <tr>
  <td>0</td>
  <td>C14</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>The desired output can be quite simple, just need both positionid and both values.</p>