Scenarios
Throughout the chapter, I will use three scenarios: Employee Organizational Chart (tree, hierarchy), Bill Of Materials or BOM (DAG), and Road System (undirected cyclic graph). Note what distinguishes a (directed) tree from a DAG. All trees are DAGs, but not all DAGs are trees. In a tree, an item can have at most one parent; in some management hierarchies, an employee can have more than one manager.
Employee Organizational Chart
The employee organizational chart that I will use is depicted graphically in Figure 9-2.
Figure 9-2. Employee Organizational Chart
To create the Employees table and populate it with sample data, run the code in Example 9-1 ...
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