title: Mysql: How to convert positive value to negative while inserting
body: <p>I have one table transaction with columns  (id, amount) all positive integers and I have another table refund with same columns but here amount is expected to be negative.
  Now I want to use Insert into command to select from transaction and insert into  refund. How can I make the amount negative while inserting. following is the query that I am trying.</p>
  
  <pre><code>INSERT INTO refund (id,amount) 
  SELECT id, amount FROM `transaction`
  </code></pre>
  
  <p>Is there any way refund.amount always takes -ve values by default.</p>