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Chapter 7. Using indices and cursors

7.14 - Summary

An index is an ordered list of all the IDs of a table. Indices are the more efficient of the two access methods employed by ADAMO (the other being selectors). With the use of cursors they may also be used to create and operate on subsets of rows of a table. The demonstrative program indices illustrates basic operations with an index; ordered access to tables, looping over indexed tables, selection of rows, use of multiple indices, navigation, and programming with both indices and selectors. The concepts introduced in this chapter are:

Index

An ordered list of the IDs of all the rows of a table. Thus a permutation of the IDs ordered according to the values of one or more attributes.

Access method

A list of IDs of a table that TAP routines can successively operate on. Can be an index or selector.

Multiple index

An index ordering a table according to the values of more than one column.

Boolean algebra on access methods

Performed by the TAP routine SOPSEL and performs boolean algebra on indices and/or selectors and puts the result in a selector.

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BR and MR - CERN PTG - ADAMO Users Guide for Version 3.3 - 11 Oct 93