Browse Prior Art Database

Algorithm for Adding a Column to a Table

IP.com Disclosure Number: IPCOM000036816D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Allan, AL: AUTHOR [+3]

Abstract

Disclosed is an algorithm for adding a column to a table in a database.

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This is the abbreviated version, containing approximately 100% of the total text.

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Algorithm for Adding a Column to a Table

Disclosed is an algorithm for adding a column to a table in a database.

To update each record of a table with null values for a newly- added column would take considerable execution time, particularly if the table is large. Yet these null values must be returned when a data record is read.

The expected length of a data record's fixed-length part is calculated from information contained in a control block associated with the table. This length reflects the addition of the new column. If a record's actual fixed-length part (stored with the record) is less than the expected value, any column or columns with offsets beyond the actual length must therefore be columns added to the table. Nulls are therefore returned as the column value(s).

The physical data record is only expanded if the record is explicitly updated.

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