title: Add and populate a column or add a persisted computed column?
body: <p>I have a DB table with 10 million rows, 5GB of data, no primary key, but a clustered index. Every day 100s of thousands of records get added. I am looking to add a new column:</p>
  
  <pre><code> ALTER TABLE dbo.CMS_hsplit ADD
       split_locIDacd  AS CONVERT(varchar(8), split) + '-' + 
       CONVERT(varchar(8), CASE WHEN loc_id = 105 THEN acd ELSE loc_id END) PERSISTED
  </code></pre>
  
  <p>The DBA assigned to this prefers to change the ETL process that loads the table instead. I know the persisted calculated field will take some time to back fill the data. Is there really a significant overhead associated with using a calculated field? </p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>The Calculated field is not expected to change for years</p>
  
  <p>If the definition did change, it would have to be retroactive</p>