title: Don't understand error message: Must declare the scalar variable "@Username".
body: <p>I have a simple script updating and showing a useraccount. (working with the management studio 2010)
  For preventing user errors I wanna use a variable in SQL (never did this before).</p>
  
  <p>When reading tutorials it should be as simple as codesample below except I i'm getting an error message. Searching the web for people with the same error, I end up seeing very complex code with the same error. Can someone give me a clue.</p>
  
  <pre><code>DECLARE @Username nvarchar(256) 
  Set @Username = 'theUsername'
  
  UPDATE aspnet_Membership
  SET IsLockedOut = 0
  WHERE UserId IN (SELECT U.UserId
  FROM aspnet_Users as U inner join aspnet_Membership M on U.UserId = M.UserId
  WHERE u.UserName = @Username)
  GO 
  SELECT U.UserId, U.UserName, M.Password, M.IsLockedOut, U.LastActivityDate
  FROM aspnet_Users as U inner join aspnet_Membership M on U.UserId = M.UserId
  WHERE u.UserName = @Username
  </code></pre>
  
  <p>Msg 137, Level 15, State 2, Line 3
  Must declare the scalar variable "@Username".</p>