Untitled query #76813

SQL

-- get list of redirect categories
set @rcat_titles = (
  select GROUP_CONCAT(page_title)
  from categorylinks
  inner join page on page_id = cl_from
  where cl_to = "All_redirect_categories"
);

select @rcat_titles;

/*select page_namespace, page_title from (
  -- this subquery get ids of matching redirect pages
  -- (and gets rid of duplicates)
  select distinct rd_from
  from (
    -- this sub-subquery exists to filter out
    -- anything except selected namespaces
    -- why not just do that in the parent query, you ask?
    -- because (hopefully) it will save a bit more computing power
    -- by not having to deal with the categorylinks on these pages.
    select rd_from
    from redirect
    inner join page on rd_from = page_id
    where page_namespace not regexp "2|3" /* no user namespace */
  ) as subq1
  inner join categorylinks on rd_from = cl_from
  where FIND_IN_SET(cl_to, @rcat_titles) > 0
  -- order by rd_from asc ((this massively massively massively increased the time to process the query)
  limit 5
) as subq2
inner join page on rd_from = page_id;*/
SQL

Checking query status...
