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Issue 11.6 ('Apple About Boxes')
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Hierarchies Using The Path Enumeration Model

Hierarchies Part Two

Issue: 11.6 (November/December 2013)
Author: Craig Boyd
Author Bio: Craig Boyd is currently an Oracle DBA for a well-known national retailer. But in his 18 years of IT experience, he has been everything from a PC Technician to iSeries System Administrator to iSeries Programmer, a Sr. Technical Lead and a Data Modeler. He lives in the great state of Texas with his wife and two kids.
Article Description: No description available.
Article Length (in bytes): 7,017
Starting Page Number: 67
Article Number: 11613
Related Link(s): None

Excerpt of article text...

In the last column we spoke about hierarchies and one approach for handling them: the adjacency model. By way of review the adjacency model stores the parent records value in the child's row. So you are always connected to one parent and it is the most immediate parent. For this issue's column we are going to continue our discussion of hierarchies, but we are going to talk about a different approach. This second approach to storing hierarchies in a database is called the path enumeration model. With the path enumeration model, rather than having the parent's id as part of the child record, you have the full path stored in a column. Here is the hierarchy we used last time:

Employee Manager

Joe {NULL}

Frank Joe

Susan Joe

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