You can get a kdb/q cookbook here:

http://code.kx.com/wiki/Cookbook

This includes a tutorial with a smartmeter concept which has several queries of increasing complexity:

http://code.kx.com/wsvn/code/cookbook_code/tutorial/

Step through this, look at the function definitions, cross-ref with the kdb reference page. Also read Q for mortals on their site:

http://code.kx.com/wiki/Tutorials

Yes it's not as accessible as other langs with loads of books, but on the plus side it's coherent, unlike c++.