title: SQL Server unique index allowing duplicates
body: <p>I am using SQL Server 2008, had a table with an id (numeric) column as the primary key.  Also had a unique index on three varchar columns. I was able to add a row with the exact same set of the three columns.  I verified it with a simple query on the values and 2 rows were returned.  </p>
  
  <p>I edited the index and added the id column.  When I tried to edit it again and remove the id column it complained that there were duplicate rows, it deleted the index but couldn't create it. </p>
  
  <p>I then clean the database of the duplicated, recreated the index with the same 3 varchars as unique and nonclustered and now it works properly, not allowing duplicates.</p>
  
  <p>Does anyone know why the uniqueness of this index was ignored?  </p>