Writing effective SQL statements

A majority of the application performance can be addressed or avoided by writing good quality SQL queries. Many-a-times, we underestimate the power of SQL writing techniques. We can write an SQL statement in many different ways to get the desired result set. The key lies in identifying the best SQL query amongst them. When an SQL query is submitted for execution, the DB2 optimizer rewrites the SQL in the most efficient way it can, but that does not mean we can get away with bad SQL queries. Inefficient SQL queries may confuse the optimizer, resulting in a suboptimal access plan. As a developer, we should always consider best practices in writing SQL queries. In this recipe, we will discuss some best practices that can help us write good quality SQL queries. We will also analyze the different ways of writing SQL statements, by comparing their access plans.

Getting Ready

We should be familiar with different tools to capture information. In this recipe, we will...