title: SQL query to get average sum of other rows and store in current rows
body: <p>I have table like this, and I want to query to store the average of others row points.</p>
  <pre><code>USER_ID        POINTS       
  ------------- --------
   a14e43e4f851  134       
   1e86e5adedbf  40     
   3c66730edf69  149  
   32e24082f97b  67   
   b33e3100a7be  124  
   274ee414ad8f  85   
   bdeef25fc797  172 
  </code></pre>
  <p>For example - for <code>user_id</code> = <code>a14e43e4f851</code>, the average sum of points should be
  <code>avg(40+149+67+124+85+172)</code> .
  PS - not taken the points (134) in calculation for user <code>a14e43e4f851</code>.</p>
  <p>Output should look like this --</p>
  <pre><code> USER_ID       POINTS   AVG     
  -------------  ------- ------
   a14e43e4f851   134     106 which is avg(40+149+67+124+85+172)  
   1e86e5adedbf   40      avg(134+149+67+124+85+172)
   3c66730edf69   149     avg(134+40+67+124+85+172)
   32e24082f97b   67      avg(134+40+149+124+85+172)
   b33e3100a7be   124     ...
   274ee414ad8f   85      ...
   bdeef25fc797   172     ...
  </code></pre>