title: Database update query for split and sum in another field using mysql
body: <p>I have one table</p>
  
  <pre><code>test
  ID       text       sum
  -----------------------
  1        1_2_3         0 
  
  2        2_3_4_5       0
  </code></pre>
  
  <p>i want to update this table as</p>
  
  <pre><code>ID       text       sum
  ------------------------
  1        1_2_3        6
  
  2        2_3_4_5      14
  </code></pre>
  
  <p>how to write the query or function/procedure.</p>