Recursion on categorylinks

SQL

with recursive subcats (depth, cat_title) as (
  select distinct 0, cl_to from categorylinks where cl_to in ('Historical_timelines')
  union all
  select depth + 1, page_title from subcats, categorylinks, page
  where cl_type = 'subcat' and cl_from = page_id and cl_to = cat_title
  and depth < 2
)

-- select count(cat_title), count(distinct cat_title) from subcats;
select min(depth), cat_title from subcats group by cat_title;

/*
select count(distinct page_namespace, page_title) from subcats
join categorylinks on cl_to = cat_title and cl_type != 'subcat'
join page on cl_from = page_id
order by page_namespace;
*/

/*
select group_concat(page_title separator '", "') from categorylinks, page
where cl_type = 'subcat' and cl_from = page_id and cl_to = 'Historical_timelines'

"Timelines_by_century", "Timelines_by_country", "Timelines_by_decade", "Timelines_by_topic", "Timelines_by_year",
"Contemporary_history_timelines", "Modern_history_timelines", "Ancient_timelines", "Timelines_of_Buddhist_history",
"City_timelines", "Culture-related_timelines", "Disaster_timelines", "Environmental_timelines", "Health-related_timelines",
"Jewish_history_timelines", "Maritime_timelines", "Personal_timelines", "Political_timelines", "Record_progressions",
"Regional_timelines", "Religion_timelines", "Science_timelines", "Technology_timelines", "Timelines_of_women_in_history",
"University_timelines", "Timelines_of_world_history"
*/
SQL

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