The book then proceeds to go into details that programmers my age have forgotten and younger programmers were never taught. The discussion on B-Tree indexes gives the usual description of how they work and balance. But then we get discussions on what causes slow indexes, the limitations of function based indexes, over-indexing, how to search for Ranges and not just simple equality. We look at when and why column order matters. There are a ton of common anti-patterns in DDL that mess up indexing and performance. The discussions of JOIN Operations (Nested Loops, Hash Join, Sort-Merge Join, Clustering Data, Sorting and Grouping, etc) is surprisingly detailed.

Perhaps the best material is the debunking of common myths that are spread out in the book: “Indexes Can Degenerate” , “Most Selective First”, "Oracle Cannot Index NULL” and “Dynamic SQL is Slow' are some examples. You will probably be surprised how many things you believe without being conscious of it.

This book is definitively worth having in the company library.

A pdf ebook is also available.

More Details:

http://sql-performance-explained.com/