title: Using MySQL to calculate difference of 2 columns to equal a 3rd column
body: <p>Ok so I'm using SQL in phpmyadmin trying to calculate the difference from 2 columns and add that value to a 3rd column. I've imported my data by CSV into the database. I'm trying to "autosum" like excel and Access in SQL database.</p>
  
  <p>My columns are "Tax Collected" - "Tax Paid" = "Tax Gain"</p>
  
  <p><a href="https://i.stack.imgur.com/ZZ0xm.png" rel="nofollow noreferrer">Imported CSV</a></p>