How to Recursively Build a Tree Structure from MySQL Hierarchical Data?

How to Recursively Retrieve MySQL Rows to Build a Tree

Problem:

Traversing a hierarchical structure, such as a bill of materials table, requires a method for recursively retrieving rows to create a nested tree representation. However, traditional SQL queries are limited in their ability to handle recursion.

Answer:

In 2011, a question was posted on DBA StackExchange seeking a MySQL solution for tree traversal. The response provided a set of stored procedures:

• GetParentIDByID: Retrieves the parent ID of a given ID.
• GetAncestry: Returns all ancestors in the hierarchy.
• GetFamilyTree: Generates the entire family tree for a given item.

Implementation:

Call GetFamilyTree(item_id) to retrieve the family tree for a specific item. This stored procedure will recursively find the parent and all ancestors, returning the results as a layered tree structure.

Example:

CREATE PROCEDURE GetFamilyTree(
   IN item_id INT
)
BEGIN

   SELECT ... # Perform recursive tree traversal

END;

Usage:

CALL GetFamilyTree(1);

This will retrieve the entire family tree for item 1 and present it in a nested format.

Benefits:

• Efficiently handles hierarchical data retrieval without the need for inefficient batch processing.
• Provides a customizable way to traverse the tree by specifying the starting node.
• Enables the generation of complex and dynamic tree structures based on database relationships.

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