O'Reilly logo

Oracle by Guy Harrison

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Chapter 11. Sorting, Grouping, and Set Operations

In this chapter we look at improving the performance of SQL operations that require Oracle to order or group data and operations that work on complete sets of data rather than on individual rows.

Oracle might need to sort data as a result of an explicit request to return data in order (for instance, ORDER BY) or as a result of an internal intermediate operation that requires the data to be in sorted order (for instance, the INTERSECT operation). Sorts can consume significant computer resources—especially memory—and have a substantial effect on query performance. Knowing when Oracle performs sorts, ways of avoiding sorts, and how to optimize sorts is, therefore, important when tuning SQL.

The ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required