Chapter 9. Tuning Table Access
In this chapter, we look at ways to improve the performance of SQL statements that access a single table. The single table query is the building block of more complex SQL queries, so understanding how to optimize the single table access is a prerequisite for improving the performance of more elaborate queries.
There are usually a number of possible access methods for any given table access. A full table scan is always an option and, depending on physical data model, there may be a number of index, partition, or cluster-based retrieval options.
The optimizer will not always choose the best access path, and you need to be able to evaluate the optimizer’s choice and sometimes encourage the use of a different access ...