Chapter 8: Making SQL Efficient in Oracle Database

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Overview

So far in Part II, SQL Code Tuning, we have covered what SQL is, the basics of efficient SQL and common sense indexing. The first three chapters are not necessarily directly Oracle related and could apply to SQL in any relational database. Now we need to look at the specifics of the Oracle database with respect to SQL code tuning and the Oracle SQL code Optimizer.

The last two chapters made use of the EXPLAIN PLAN command extensively for demonstration purposes. All the types of data access shown in query plans will be described in detail in this chapter.

In this chapter we will try to understand how Oracle Database executes SQL code and how that SQL code can be tuned from a purely Oracle Database perspective. There will be some crossover in this chapter with configuration tuning. Numerous Oracle Database configuration parameters affect the way that SQL code is executed. The essence of this chapter is to discover what exactly Oracle Database does when an SQL statement is submitted to the Oracle Database engine. There are specific steps:

  • Parsing.   Parsing is the verification of SQL code syntax and interpretive compilation into a form understandable by the Oracle Database engine.

  • Optimization.   The Optimizer attempts to automatically pick the fastest method of execution for an SQL code statement.

  • Execution.   SQL code statements are executed in various forms and by various routes, decided by the Optimizer.

  • Return of results.   Results are passed back to the calling process.

Let's start with some brief descriptions.



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Oracle High Performance Tuning for 9i and 10g
Oracle High Performance Tuning for 9i and 10g
ISBN: 1555583059
EAN: 2147483647
Year: 2003
Pages: 164

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