Database Reference
In-Depth Information
in the owner node. Additionally, a record in the member node cannot exist without being
related to an existing record in the owner node. For example, a client must be assigned to
an agent, but an agent with no clients can still be listed in the database.
Figure 1.4
shows a
diagram of a basic set structure.
Figure 1.4. A basic set structure
One or more sets (connections) can be defined between a specific pair of nodes, and a
single node can also be involved in other sets with other nodes in the database. In
Figure
structure. It is also related to the ENGAGEMENTS node via the Schedule set structure.
Along with being related to the CLIENTS node, the ENGAGEMENTS node is related to
the ENTERTAINERS node via the Perform set structure.
A user can access data within a network database by working through the appropriate set
structures. Unlike the hierarchical database, where access must begin from a root table, a
usercanaccessdatafromwithinthenetworkdatabase,startingfromanynodeandworking
backward or forward through related sets. Consider the Agents database in
Figure 1.3
once
again. Say a user wants to find the agent who booked a specific engagement. She begins
bylocatingtheappropriateengagementrecordintheENGAGEMENTSnode,andthende-
termines which client “owns” that engagement record via the Schedule set structure. Fin-
ally, she identifies the agent that “owns” the client record via the Represent set structure.
The user can answer a wide variety of questions as long as she navigates properly through
the appropriate set structures.
