Inside Oracle Sorting

Oracle sorting is a very important component of Oracle tuning, yet sorting optimization is often overlooked.

An Oracle database will automatically perform sorting operations on row data under the following circumstances:

• When an index is created
• When using the ORDER BY clause in SQL
• When using the GROUP BY clause in SQL

There are several ways to sequence Oracle output rows:

• Oracle internal sort (in sort_area_size or TEMP tablespace)
• Retrieve the rows in pre-sorted order (using an index)

Using a third-party sort product - For shops that have to sequence millions of rows of output on an hourly basis, external sort products can be faster than using Oracle to sort the data.