Database Reference
In-Depth Information
The Hierarchical Database Model
Data in this type of database is structured hierarchically and is typically diagrammed as an
inverted tree. A single table in the database acts as the “root” of the inverted tree and other
tables act as the branches flowing from the root.
Figure 1.1
shows a diagram of a typical
hierarchical database structure.
Figure 1.1. Diagram of a typical hierarchical database
Agents Database
In the example shown in
Figure 1.1
,
an agent topics several entertainers,
and each entertainer has his own schedule. An agent also maintains a
numberofclientswhoseentertainmentneedsaremetbytheagent.Acli-
ent topics engagements through the agent and makes payments to him
for his services.
A relationship in a hierarchical database is represented by the term
parent/child.
In this
type of relationship, a parent table can be associated with one or more child tables, but a
single child table can be associated with only one parent table. These tables are explicitly
linked via a pointer or by the physical arrangement of the records within the tables. A user
accesses data within this model by starting at the root table and working down through the
