Crystal Reports for Rational Application Developer Designer Guide

Characteristics of the data needed for hierarchical grouping

You can group data in a report to show hierarchical relationships. When you group data hierarchically, Crystal Reports sorts information based on the relationship between two fields.

A hierarchical relationship must be inherent in the data that you use for the report:

Parent and child fields must be of the same data type for the program to recognize a relationship between them.
The data in the parent field must be a subset of the data in the child field.
For the top level of a hierarchy to appear in a report, the value must appear in the child data, and the corresponding row in the parent data must be empty.
There cannot be any circular logic in the data (that is, if B reports to A, and C reports to B, then A cannot report to C).

For example, if you want to show the hierarchical relationship of the people who work in a department, you could group data by employee name (the child field) and specify the hierarchy by using the field that lists whom the employee reports to (the parent field). Your database tables might look like the following example.

Employee (child)	Supervisor (parent)
Jane	Thomas
Mina
Gerard	Thomas
Albert	Thomas
Thomas	Mina
Beth	Thomas
Teresa	Thomas
Gareth	Thomas
Valerie	Thomas
Gillian	Mina
Frances	Gillian
Ruth	Gillian
Margaret	Mina
Paul	Margaret
Charles	Margaret

The Employee and Supervisor fields contain overlapping data that implies a hierarchical relationship. There are 15 unique employee names, with four of these names also appearing as supervisors (Mina, Thomas, Gillian, and Margaret). Three employees report to Mina, seven employees report to Thomas, two employees report to Gillian, and two employees report to Margaret.

Note: Mina has no corresponding Supervisor. This data implies that Mina is a top-level supervisor who does not report to anyone else in this table.

In the report, the hierarchical groupings may be represented various ways. For example:

First level of the hierarchy	Second level	Third level
Mina
	Thomas
		Jane
		Gerard
		Albert
		Beth
		Teresa
		Gareth
		Valerie
	Gillian
		Frances
		Ruth
	Margaret
		Paul
		Charles

If you group a Crystal Reports report on the Employee field, you can further sort the data to show the hierarchical relationship between these employees and their supervisors.

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