title: Regular Expression that Validates Decimal (18,3)
body: <p>I need a regular expression that can validate <code>Decimal (18,3)</code>, meaning a precision of 18, and a scale of 3.</p>
  
  <p>It would need to pass the following criteria:</p>
  
  <ul>
  <li>Max number of digits before comma is <code>15</code> </li>
  <li>Max number of digits after the comma is <code>3</code></li>
  </ul>
  
  <p><strong>Valid Examples</strong>:</p>
  
  <pre class="lang-none prettyprint-override"><code>123456789.123
  123456789123456.12
  12345.1
  123456789123456
  </code></pre>
  
  <p><strong>Not Valid Examples</strong>:</p>
  
  <pre class="lang-none prettyprint-override"><code>1234567891234567
  123.1234
  1.12345
  .1234
  </code></pre>
  
  <p>How can I achieve this?</p>