title: nchar vs nvarchar performance
body: <p>How do you decided whether to use <code>nvarchar</code> or <code>nchar</code> ?</p>
  
  <p>For instance I have noticed that the default membership database created by sqlmembership provider declares the Email column to be type nvarchar(256)</p>
  
  <p>To me that seems like an unnecessarily large maximum value for an email column. I would suspect in normal circumstances emails longer than 40 or 50 characters would be pretty rare.</p>
  
  <p>But as data such as email addresses vary in length should they always be stored as a nvarchar so as to eliminate redundant space?</p>
  
  <p>If using nvarchar for an email column. In the event of an email address being changed, if the new email is longer than the previous email will this cause many page splits and therefor much of a performance cost?</p>
  
  <p>Would you ever consider using nchar(40) for an email address and compromising loss of storage space in return for no page split performance costs?</p>
  
  <p>Or would using nchar(40) significantly increase database size thereby cause other performance hits on query speed?</p>
  
  <p>Would 'only use nchar when you know the size of data to fill the column' be a reasonable rule to follow?</p>