A few things to consider before migrating to SQL 2008

The good news for developers is that a large majority of SQL 2008 functionality and behavior is backward compatible with SQL 2005. 

However, deprecated, discounted, and changed features should be reviewed before moving a SQL 2005 database to a SQL 2008 server.  For more information about SQL backward compatibility, please visit http://msdn.microsoft.com/en-us/library/cc707787.aspx.

Microsoft also provides a SQL Server 2008 Upgrade Advisor that can be used to analyze a SQL 2005 database to check for potential compatibility issues.  This is a stand-alone application, and it can be downloaded for free at http://www.microsoft.com/downloads/details.aspx?FamilyId=F5A6C5E9-4CD9-4E42-A21C-7291E7F0F852&displaylang=en.

Barring any compatibility issues determined above, a SQL 2005 database should work out-of-the-box on a SQL 2008 server.

For more information about SQL Server 2008, please also see:

Microsoft SQL Server 2008 product page

SQL Server Developer Center

SQL Server 2008 Overview

What's New in SQL Server 2008

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