title: postgresql : regexp_substr - get sub string between occurrence of delimiters
body: <p>I have these strings:</p>
  <pre class="lang-none prettyprint-override"><code>[{&quot;Name&quot;:&quot;id&quot;,&quot;Value&quot;:&quot;Window_Ex_kebklipecbcegiocpa_widget_open&quot;
  [{&quot;Name&quot;:&quot;id&quot;,&quot;Value&quot;:&quot;Window_Ex_kebklipecbcegiocpa_widget_close&quot;
  [{&quot;Name&quot;:&quot;id&quot;,&quot;Value&quot;:&quot;Window_Ex_kebklipecbcegiocpa_widget_mid_value&quot;
  </code></pre>
  <p>and I'm trying to extract only the parts after the third <code>_</code>, until the end of the string (which ends always with <code>&quot;</code>)</p>
  <pre class="lang-none prettyprint-override"><code>widget_open
  widget_close
  widget_mid_value
  </code></pre>
  <p>I'm using postgresql, and wanted to use the regexp_substr syntax, in order to extract it.
  Thanks!</p>