title: view with clause for only one column
body: <p>I need to create a view with 3 columns, the first two there are no problems because they are simple sums with groupings by date...for the third I need to add only some values ​​from the initial table, how can i solve? use two where? or two condition for clause? . For example:</p>
  
  <pre><code>T1
  id||amount||cod_pay||reg_date
  1 ||10.00 ||SDD    || 2019-08
  2 ||5.00  ||BON    || 2019-08
  3 ||15.00 ||SDD    || 2019-07
  4 ||10.00 ||BOL    || 2019-06
  5 ||40.00 ||SDD    || 2019-06
  6 ||110.00||BON    || 2019-06
  
  VIEW
  reg_date||month_amount||sdd_month_amount
  2019-08 ||15.00       ||10.00           
  2019-07 ||15.00       ||15.00           
  2019-06 ||160.00      ||40.00   
  </code></pre>
  
  <p>I don't know if it's clear, I hope so.
  Thanks for the support.</p>