SQL tuning book by Dan Tow
This is one of the books I recommend to people, who want to learn more about performance tuning. What I like about the book is that it explains both the why (general principles) and then the how (on Oracle, SQL Server and DB2).
In the first part of Dan Tows book you will learn about
join algorithms (hash, loop, sort-merge)
execution plans and how to achieve them
how to control execution plans
Then Dan Tow spends the rest of the book introducing his patented method of transforming a SQL query into a directed graph. From this graph, one can deduce the most efficient execution plan, especially which join order will be most efficient. I personally used this method in the beginning of my career as a consulting with database performance tuning skills.
The book concludes with a chapter on methods to tune expensive queries if SQL cannot help.
I can only highly recommend this great book.
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