— @@version – Get version, product version/release, 32 or 64 bit
SELECT @@VERSION
Output:
Microsoft SQL Server 2005 – 9.00.1399.06 (Intel X86) Oct 14 2005 00:33:37 Copyright (c) 1988-2005 Microsoft Corporation Developer Edition on Windows NT 5.2 (Build 3790: Service Pack 2)

— SERVERPROPERTY('productversion') – Product version/release
— SERVERPROPERTY ('productlevel') – Product level (RTM –
— SERVERPROPERTY ('edition') – Product Edition (Developer, Standard, Enterprise)
— Documentation on SERVERPROPERTY http://msdn.microsoft.com/en-us/library/ms174396.aspx
SELECT SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY ('edition')
Output:
9.00.1399.06 RTM Developer Edition