UPDATE OPERATIONS FOR HIERARCHICAL STRUCTURES IN THE NESTED SETS MODEL

Abstract

The article examines an approach to storing hierarchical data in relational databases using the Nested Sets model. The fundamental principles of this model, its advantages and disadvantages compared to other methods, particularly the Adjacency List, are analyzed. Special attention is given to subtree movement and node deletion algorithms within the hierarchical structure, including the update of lft and rgt values. Examples of SQL queries for subtree movement and node deletion are provided. The Nested Sets model is advisable for use in relational databases when efficient querying of hierarchical data is required. However, inserting, moving, and deleting nodes require updating multiple records due to changes in lft and rgt values. Even if restructuring is performed infrequently, it can be very slow for large trees. Understanding the restructuring process helps determine whether Nested Sets should be used in a specific case or if alternative approaches to storing hierarchical data in relational databases should be considered.