title: UPDATE to remove duplicates from comma-separated list
body: <p>In my Postgres db, I have a table with some columns where one column <code>B</code> has values as follows: </p>
  
  <pre><code>A      B
  a1     b0, b1, b1
  a2     b2, b3
  a3     b4, b4, b5, b5
  </code></pre>
  
  <p>My expected output should be like this: </p>
  
  <pre><code>A      B
  a1     b0, b1
  a2     b2, b3
  a3     b4, b5
  </code></pre>
  
  <p>Is there a simple <code>UPDATE</code> in Postgres to do this?</p>