title: I want to use CASE statement to update some records in sql server 2005
body: <pre><code>UPDATE dbo.TestStudents  
  SET LASTNAME = 
  ( CASE  
  WHEN (LASTNAME = 'AAA') THEN 'BBB' 
  WHEN (LASTNAME = 'CCC') THEN 'DDD' 
  WHEN (LASTNAME = 'EEE') THEN 'FFF' 
  ELSE  (LASTNAME)
  END )
  </code></pre>
  
  <p>The statement work for the purpose but the else condition scan through every record in the table. Is there any way I can leave the unaffected rows as they are?</p>