title: How to get total as a separate total Column in sql
body: <p>I am trying to get Total_Paid column </p>
  
  <pre><code>Product     Timestamp   Paid                  Total_Paid
  A             201801    12                     36
  A             201802    11                     36
  A             201803    13                     36
  B             201801    10                     45
  B             201802    15                     45
  B             201803    20                     45
  </code></pre>
  
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