How to Retrieve All Subdirectories of a Given Directory Using a Single Recursive SQL Query?

Recursive Queries for Retrieving Subdirectories

Consider a scenario where you have a table named folders_table that captures a directory structure with columns for id_folder, id_folder_parent, and folder_name. To retrieve all subdirectories of a specific directory using a single SELECT query, you need to adopt a recursive approach. The following steps provide guidance:

1. Alter the Database Structure: Modify the folders_table to include a level column, which will indicate the depth of each folder within the hierarchy. Start with level 1 for the root directory and increment for each level below.
2. Create a Recursive Query: Utilize a recursive CTE (Common Table Expression) to traverse the directory structure. The query should start with the desired root folder and recursively retrieve all its subdirectories, including their level.
3. Filter and Join: Constrain the query to only include the subdirectories of the desired depth. Join it with the original folders_table to retrieve additional folder details if needed.

This approach enables you to retrieve a tree of subdirectories up to any depth with a single query. Refer to the resources provided in the provided answer for detailed implementation guidelines.

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