Chapter 24 - Regions, Runs, Gaps, Sequences, and Series

Abstract

The first rule in a relational database is that all relationships are shown in tables by values in columns. This means that things involving an ordering must have a table with at least two columns. One column—the sequence number—is the primary key; the other column has the value that holds that position in the sequence. The sequence column has consecutive unique integers without any gaps in the numbering. Instead of looking for a region, numbering the regions is wanted in the order in which they appear. Another form of query asks whether there is an overall trend between two points in time bounded by a low value and a high value in the sequence of data. Runs are informally defined as sequences with gaps. The summation of a series builds a running total of the values in a table and shows the cumulative total for each value in the series. To manipulate a list of values, to chang their sequence position numbers is required. The simplest such operation is to swap two values in the table.