WITH hc AS (

    -- list of pages under category:隐藏分类

    SELECT p.page_id, p.page_title

    FROM categorylinks c

    LEFT JOIN page p ON (c.cl_from = p.page_id)

    WHERE c.cl_to = "隐藏分类"

)

-- list of categories under each page

SELECT hc.page_id, hc.page_title, c.cat_pages, COUNT(*) AS cat_count

FROM hc

LEFT JOIN categorylinks c2 ON (hc.page_id = c2.cl_from)

LEFT JOIN category c on (c.cat_title = hc.page_title)

GROUP BY 1, 2, 3

HAVING COUNT(*) = 1

ORDER BY 3 DESC