title: regular expression to return specific pattern from a string
body: <p>I am a beginner to oracle regular expression. I have following string</p>
  
  <pre><code>'Critical fix ;,DI 2.2.1 new fixes , DI 2.2.2 maintenance plan , DI 3.2.1 new patch'
  </code></pre>
  
  <p>From above string I want to get output as below using regexp_substr.</p>
  
  <pre><code>DI 2.2.1,DI 2.2.2,DI 3.2.1
  </code></pre>
  
  <p>The string in question can have multiple occurrences (DI x.x.x) and using regular expression it should return a command separated string as described in the output. 
  Please help</p>