USE enwiki_p;

SELECT unspaced_page_title, child_titles

FROM (

SELECT 

  unspaced_page_title,

  COUNT(DISTINCT primary_page_title) AS num_child_titles, # Using DISTINCT primary_page_title excludes page titles that redirect to the same page.

  GROUP_CONCAT(page_title SEPARATOR "; ") AS child_titles

FROM (

  SELECT

    page_title,

    REPLACE(LOWER(page_title), "_", "") AS unspaced_page_title,

    CASE

      WHEN page_is_redirect THEN rd_title # Possibly inaccurate results with redirects that go outside of template-space, but those are rare.

      ELSE page_title 

    END AS primary_page_title

  FROM page

  LEFT JOIN redirect ON rd_from = page_id

  WHERE

    page_namespace = 10

) AS subquery1

GROUP BY unspaced_page_title

) AS subquery2

WHERE num_child_titles > 1