title: concatenate DISTINCT string values in pentaho data integration
body: <p>I am new to pentaho data integration. How can i concatenate distinct string values ?</p>
  
  <pre><code>bse_id values
  100     A1
  100     A1
  100     A2
  150     A1
  150     B1
  150     C1
  150     C1
  </code></pre>
  
  <p>putput should be</p>
  
  <pre><code>bse_id values
  100    A1,A2
  150    A1,B1,C1
  </code></pre>
  
  <p>In Mysql, i can use 
      select bse_id,group_concat(distinct values) from table group by 1;</p>
  
  <p>In SPOON, i have tried group_by step and memory group_by 
  both are resulting in duplicate values.
  I'm getting output as</p>
  
  <pre><code> bse_id values
      100    A1,A1,A2
      150    A1,B1,C1,C1
  </code></pre>
  
  <p>Please help me in removing the duplicates.</p>