From the February 2012 Issue of Prestwood eMag
Aggregators and their Scope: A Paradox for DOS Perspective
Posted 3/19/2003 on 3/19/2003 and updated 6/9/2008
Take Away: Discussion of aggregators in Paradox for Windows reports as they relate to Paradox for DOS.


You may have heard the summary fields in Paradox for Windows referred to as aggregators. This is because there are now new ways to aggregate, or combine, values in fields. Some differences in this area between Paradox for Windows and earlier versions of Paradox include the addition of Standard Deviation, Variance, First, Last, and Previous to the expected Count, Sum, Max, Min, and Average; the ability to place aggregator fields in headers as well as footers; and the addition of Unique as an option alongside the standard Per Group and Overall (more appropriately renamed Normal and Cumulative).

The scoping rules have also changed a little due to the increased power of the report generator and underlying data model. By scoping I mean the scope, or range, of records to include when calculating a summary; in other words, which records should be used when combining, or aggregating, values.

The scoping rules are basically the same as Paradox Dos' report generator in Report footers, Page footers, and Group footers except that placing a summary field in a header will give the same result as its corresponding footer. Anything you would expect to normally work in a footer can also be placed in a header.

In the Record Band (formerly the Table Band or Form Band), the scope of an aggregate on a field in the master table would be the whole table, while the scope of an aggregator on a field in a detail table would be the restricted view (group) for that master record.

KB Post Contributed By Mike Prestwood:

Mike Prestwood is a drummer, an author, and creator of the PrestwoodBoards online community. He is the President & CEO of Prestwood IT Solutions. Prestwood IT provides Coding, Website, and Computer Tech services. Mike has authored 6 computer books and over 1,200 articles. As a drummer, he maintains and has authored 3 drum books. If you have a project you wish to discuss with Mike, you can send him a private message through his PrestwoodBoards home page or call him 9AM to 4PM PST at 916-726-5675 x205.

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