Joe Celko's Trees and Hierarchies in SQL for Smarties

Joe Celko's Trees and Hierarchies in SQL for Smarties

The Morgan Kaufmann Series in Data Management Systems
2004, Pages 199-213
Joe Celko's Trees and Hierarchies in SQL for Smarties

Chapter 12 - Hierarchical Database Systems (IMS)

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Publisher Summary

The chapter focuses on hierarchical database using IMS database language. IMS is the most important prerelational technology that is still in wide use today. IMS from IBM is stable, well-defined, scalable, and very fast for what it does. The IMS software environment can be divided into five main parts: database, data language I (DL/I), DL/I control blocks, data communications component (IMS TM), and application programs. The chapter discusses these components. In comparison with SQL, IMS is fast, saves storage, and is tuned for one set of applications, whereas SQL is simple, portable, and flexible. The chapter also illustrates how a hierarchical structure looks, and designs two very simple databases to store information for the courses and students in a college. One database will store information on each department in the college and the second will contain information on each college student. In a hierarchical database, an attempt is made to group data in a one-to-many relationship. The chapter also designs these databases so that data that is logically dependent on other data is stored in segments that are hierarchically dependent on the data.

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