Where do you get Example/Sample Databases from?
For MySQL, there are sample databases used (frequently in examples) and they are to be found here (rather confusingly) in the "documentation" section, under "other docs" - here. I'm afraid that I can't help with SQL Server, but I'm sure that there are others here who can.


Example Databases Title  Download DB HTML Setup Guide    PDF Setup Guide
employee data (large dataset, includes data and test/verification suite)      Launchpad
world database  
sakila database
menagerie database


You might also want to check out my reply here to a poster who was looking for NoSQL datasets (shouldn't make a difference whether it's NoSQL or not).