title: Immutable SQL columns
body: <p>Is it possible to mark a column <code>immutable</code> in MSSQL?</p>
  
  <p>Seems like it would be a useful DDL feature; once a value is set in a row ('row' being defined as a specific relation of values to a primary key), it could not be changed without deletion of the row.</p>
  
  <p>Obviously (like most things) this is more than doable in the application layer, but half the fun of SQL DDL is error-checking your application code.</p>