Hierarchical models make the most sense where the primary focus of information gathering is on a concrete hierarchy such as a list of business departments, assets or people that will all be associated with specific higher-level primary data elements. 4 Examples of hierarchical data represented as relational tables An organization could store employee information in a table that contains attributes/columns such as employee number, first name, last name, and department number.
While some IBM and Microsoft models are still in use, many other types of business databases use more flexible models to accommodate more sophisticated types of data management. Another example of the use of hierarchical databases is Windows Registry in the Microsoft Windows operating systems. You can think of these lines or branches as a connection to the next level of more specific information. A hierarchy is just an arrangement of 'things' called nodes, and the nodes are connected by lines or 'branches'. Hierarchical databases were popular in early database design, in the era of mainframe computers. For example, many old timers still call creating an index on customernumber as, 'inverting a file on customernumber'. Thus, the problem raised above in the sales order processing will not arise in the network. (b) Network model: In the network model of database, there are no levels and a record can have any number of owners and also can have ownership of several records. For example, where each individual person in a company may report to a given department, the department can be used as a parent record and the individual employees will represent secondary records, each of which links back to that one parent record in a hierarchical structure. Figure 9.4 shows the hierarchical model of data for a sales order processing application. Its limitations mean that it is confined to some very specific uses. The idea behind hierarchical database models is useful for a certain type of data storage, but it is not extremely versatile.
Techopedia Explains Hierarchical Database
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