title: How to set default value to getdate() with sql server
body: <p>I'm using the sequel ruby orm with sql server.
  I would like to know how to set the default value of a datetime field to the sql server function getdate() in a migration:</p>
  
  <pre><code>create_table(:table) do
    primary_key :id
    datetime :last_update, null: false, default: ???
  end
  </code></pre>
  
  <p>Thanks for your help :-)</p>