title: insertion in a self referenced table
body: <p>If I have a table</p>
  
  <pre><code>Table
  {
  ID int primary key identity,
  ParentID int not null foreign key references Table(ID)
  }
  </code></pre>
  
  <p>how does one insert first row into a table?</p>
  
  <p>From a business logic point of view not null constraint on ParentID should not be dropped.</p>