Sometimes you do not need the full result of an SQL query but only the
first few rows—e.g., to show only the ten most recent messages. In this
case, it is also common to allow users to browse through older
messages—either using traditional paging navigation or the more modern
“infinite scrolling” variant. The related SQL queries used for this function
can, however, cause serious performance problems if all
messages must be sorted in order to find the most recent ones. A pipelined
by is therefore a very powerful means of optimization for
This chapter demonstrates how to use a pipelined
order by to efficiently retrieve partial results.
Although the syntax of these queries varies from database to database, they
still execute the queries in a very similar way. Once again, this
illustrates that they all put their pants on one leg at a time.