Joe Celko's SQL for Smarties, 5th Edition

Chapter 32

Sub-sequences, Regions, Runs, Gaps, and Islands

Abstract

The groups in a GROUP BY do not depend on any orderings. But you will often want to make other groupings which depend on an ordering of some kind. Examples of this sort of data would be ticket numbers, time series data taken at fixed intervals, and the like which can have missing data or sub-sequences that are of interest.

Keywords

Sub-sequences

Regions

Runs

Gaps

Islands

Linear interpolation

NULL

We have already talked about the GROUP BY clause in queries. The groups in a GROUP BY do not depend on any orderings. But you will often want to make other groupings which depend on an ordering of some kind. Examples of this sort of data would be ticket numbers, time series data ...