Technical References

However, in this case, a third table, called a cross-reference table, actually links the tables so
the relationship is actually one-to-many. For example, Figure 3 shows how the Skill Group
Member table acts as a cross-reference table for the Agent and Skill Group tables.
Figure 2: Cross Reference
The Skill Group Member table contains one record for each member of each skill group. It has
one-to-many relationships with both the Agent table and the Skill Group table. This avoids a
direct many-to-many relationship between the Agent and Skill Group tables.
Key Fields
One or more fields within a table can form a key. Keys are the fields used most commonly to
locate specific records. Usually the fields that make up a key are defined as NOT NULL (meaning
they cannot take the NULL value), but there are many exceptions.
Most tables have a primary key. For example, the PeripheralID field is the primary key for the
Peripheral table.
An example of a foreign key is the PeripheralID field in the Agent table. You can use this key
to find all agents associated with a specific peripheral.
The Agent table contains two alternate keys: the EnterpriseName field, and the combination of
the PeripheralID and PeripheralNumber fields. A value for either of these keys uniquely identifies
an agent.
Database Schema Handbook Cisco ICM/IPCC Enterprise & Hosted Editions 7.2(2)
9
Chapter 1: Introduction
General Concepts