title: SQL Server Component Constraint or Constraint for more than 1 column
body: <p>I want to create a table with operational details like:</p>
  
  <pre><code>CRAETED_ON DATETIME NOT NULL DEFAULT GETDATE(),
  CREATED_BY VARCHAR(10) NOT NULL,
  DELETED_ON DATETIME NULL,
  DELETED_BY VARCHAR(10) NULL
  </code></pre>
  
  <p>I want to put constraint <code>IF DELETED_ON</code> is updated then they should provide the <code>DELETED_BY</code>.</p>
  
  <p>BOTH should be NULL or both should not be NULL are allowed. One NULL &amp; other NOT NULL is not allowed.</p>