From Trees to Tables: Storing Hierarchical Data in Relational Databases

This article discusses different techniques for storing hierarchical data in relational databases, focusing on the Adjacency List, Nested Sets, and Materialized Path models. The Adjacency List method, while easy to implement, can be inefficient for finding descendants. Nested Sets use left and right indexes for efficient subtree retrieval and ancestor/descendant checks but can be complex for insertions and deletions. Materialized Path stores the path from the root to each node, making updates simpler but potentially leading to long paths and inefficient subtree retrieval. The choice of technique depends on factors like data size, read/write frequency, and complexity preferences. The article provides insights into the pros and cons of each method and offers resources for implementation. Ultimately, the best approach varies based on specific requirements, balancing performance, storage, complexity, and flexibility considerations.