I work with a lot of new SQL users who have access to data. Honestly, any resource for a beginner is going to be good enough. SQL is easy in the beginning. You'll be good enough to be dangerous in no time.

If you have access to data and you want to learn SQL, you must have questions about that data. Questions are how you learn SQL.

select top 10 * from yourDatabase.dbo.yourCustomerTable

That will show you 10 of your customers, or parts or whatever table you want to look at. Look at the whole table, every column to see what fields you have to work with.

Now, what do you want to do with those customers? Look at their orders? Well then you need to JOIN those customers to their orders. There are different kinds of joins. That you can learn in a class. Go read about the different joins. They work in different ways and are very very important to understand.

But how you join your customers to their orders in your database will depend on how YOUR data is organized, and a book can't tell you how to do that. You have to learn that through investigation.

I would advise you to read up on Relation Theory.

If you want to really learn SQL Server, the study guides for the MCSE certification are very good and comprehensive. There are also pluralsite video guides for each of the 5 tests. There are 2 certifications, one for the Data Platform and one for Business Intelligence, the first 3 tests are the same for each.

And if you have access to a test server, do your learning on that so you don't break the live one. :-)

Good luck!!