SQL Tuning [Electronic resources] نسخه متنی

Objectives of This Book

I designed this book to equip you to respond
correctly to any SQL tuning problem. The narrowest and most common
solution to a SQL tuning problem is a prescription for some
combination of changes to the database (for example, new indexes)
and, more often, changes to the SQL itself. These changes allow the
formerly slow statement to run faster, with no changes in
functionality and no change in the calling application, except in the
SQL itself. This common solution is especially attractive, because it
is usually simple and it rarely has unintended side effects.

Occasionally, when you analyze a SQL tuning problem, you discover
symptoms that generally indicate a subtle functional defect that goes
hand in hand with the performance defect. The method of tuning
analysis I describe makes those subtle functional defects
particularly easy to identify and describe, and helps you prescribe
solutions that fix corner-case functional defects as a side effect of
your performance analysis. This book focuses mainly on tuning,
however. If you are on Oracle, you can find good advice on getting
your SQL functionally correct in Sanjay Mishra's and
Alan Beaulieu's book


Mastering
Oracle SQL (O'Reilly & Associates,
Inc.).

Rarely, a SQL tuning problem cannot be solved just by speeding up one
query; the query returns too many rows, or it runs too frequently to
ever run as fast as it must, even fully optimized. For these rare
problems, I describe systematic solutions in the application layer
that change the problem model, creating a new problem that has ready
solutions.