title: Add nullable column to SQL Server with default value of null
body: <p>I want to add a nullable boolean column to an existing table with default value of null.</p>
  
  <p>I have used this bit of script but it does not set the default value to null. it sets it to 0 instead. </p>
  
  <pre><code>ADD newColumnName BIT NULL
      CONSTRAINT DF_tableName_newColumnName DEFAULT(null)
  </code></pre>