title: Default value is GUID in SQL Server table column
body: <p>I need to add a column to an already existing table and set it to be the primary key. I use other software to add new data. Why does the column <code>GIANGGUID</code> have the value <code>00000000-0000-0000-0000-000000000000</code> ?</p>
  
  <pre><code>ALTER TABLE dbo.Test 
     ADD [GIANGGUID] UNIQUEIDENTIFIER DEFAULT NEWID() PRIMARY KEY;
  </code></pre>