The total file size under the Library Back-Up Project on Wikimedia Commons

SQL

SET @basecat = 'Library_back_up_project';
SET max_recursive_iterations = 2;

WITH RECURSIVE subcats (subcat, catpath, depth) AS
(
  SELECT
    cl_to AS subcat,
    REPLACE(cl_to, '_', ' ') AS catpath,
    0 AS depth
  FROM categorylinks
  WHERE cl_from = (SELECT page_id FROM page WHERE page_title = @basecat AND page_namespace = 14)

  UNION

  SELECT
    cl.cl_to,
    CONCAT(sc.catpath, ' > ', REPLACE(cl.cl_to, '_', ' ')),
    sc.depth + 1
  FROM categorylinks cl
  JOIN subcats sc ON cl.cl_from = sc.subcat
  JOIN page p ON cl.cl_from = p.page_id
  WHERE p.page_namespace = 14
)
SELECT DISTINCT subcat AS category, depth, catpath AS 'category path'
FROM subcats
ORDER BY depth, subcat;

SQL

Checking query status...