AdventureWorks is a Sample Database shipped with SQL Server and it can be downloaded from CodePlex site. AdventureWorks has replaced Northwind and Pubs from the sample database in SQL Server 2005.The Microsoft team keeps updating the sample database as they release new versions.

For SQL Server 2012 RTM Samples AdventureWorks Database is released:

• AdventureWorks2012 Data File
• AdventureWorks2012 Case Sensitive Data File

You can download either of the datafile and create database using the same. Here is the script which demonstrates how to create sample database in SQL Server 2012.

CREATE DATABASE AdventureWorks2012
ON (FILENAME = 'D:\AdventureWorks2012_Data.mdf')
FOR ATTACH_REBUILD_LOG ;


Please specify your filepath in the filename variable. Here is the link for additional downloads.

Reference: Pinal Dave (http://blog.sqlauthority.com)