Nice reading about SQL indexing and SQL tuning for developers

My colleagues shared with me a link to an online SQL indexing and tuning tutorial (a guide to database performance by Markus Winand) which I think is worth reading. "Indexed ORDER BY", "Searching for ranges" - those are few sample topics described in the book. Different DBMS are covered - MS SQL, Oracle and others. You can also check your SQL tuning knowledge by taking a short online test.