title: Rails Migrations - Modify rows based on condition
body: <p>I need to update a table data in database using RAILS migrations. </p>
  
  <pre><code>Sample:
  Table: Table_A(Col_A(number), Col_B(varchar),...)
  Query: UPDATE Table_A SET Col_B = "XXX" where Col_B = "YYY"
  </code></pre>
  
  <p>What would be the best way to do this using RAILS Migrations. I am not even sure if RAILS migrations is the way to go for updating data in database. Any explanation would be helpful.</p>