The Product Category level might contain members
such as Hardware, Software, and so forth. The Product Subcategory level might
contain members such as Peripherals, Motherboard, Video Cards, Games, Business
Applications, and so on. The members at each level are unique; in other words,
a Product Subcategory is not also a Category. An individual product is not also a
Product Group. There is a clearly defined hierarchy and all individual products are
found at the lowest level of that hierarchy, and products are found at higher levels.
Contrast that with a standard organizational chart. At the top is the President
or Chief Executive Officer. Below that is a group of Vice Presidents. Next come
Directors, Managers, and employees. However, one Vice President might have
two Directors, another might have five, and a third Director might not have any. In
addition, some parts of the business might have Managers and then Team Leaders,
while other departments don??™t use team leaders. In other words, there??™s no welldefined
hierarchy, so a table can??™t have a set number of columns to represent the
levels in an organization.
In addition, everyone is an employee. The CEO is an employee and thus needs
to be in the employee table. Each Vice President, Director, and Manager is also an
employee. This means that there will be individual employees at each level of the
hierarchy, and that the hierarchical structure is not well defined.
The classic way to handle this in a relational sense is to have an Employee ID
field act as the primary key on the table.
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