To display compatibility levels that can be set, 60 – 6.0, 65 – 6.5, 70 – 7.0, 80 – SQL Server 2000, 90 – SQL Server 2005
exec sp_dbcmptlevel
Output: Valid values of the database compatibility level are 60, 65, 70, 80, or 90.

To display compatibility level of the database
exec sp_dbcmptlevel ‘AdventureWorks’
Output: The current compatibility level is 90.

To change compatibility level of the database
exec sp_dbcmptlevel ‘AdventureWorks’, 90
Output: DBCC execution completed. If DBCC printed error messages, contact your system administrator.