title: Adding a previous value with the current value in mysql
body: <p>I have two columns namely zone and total_bill_amount, I want to add the previous values with the current value of a column..I have used </p>
  
  <pre><code> select  zone, total_bill_amount, sum(total_bill_amount) as Total_Bill
   from Cal_Amount  
   where cluster_number = 'clust 2' 
   group by zone,total_bill_amount;
  
   1. zone       total_bill_amount   Total_Bill                           
  
   2. ABC          45                    45                               
  
   3. PQR          78                    123                              
  
   4. XYZ          16                    139
  </code></pre>
  
  <p><code>45 = 45                                                                                                45+78 = 123                                                                       123 + 16 = 139</code>                                                                    </p>