SQL to be able to have a sorting column with category

sortable.sql

; removal
UPDATE page
  , (SELECT category_id as oldcategory, page_order as oldorder FROM page WHERE id = :pgid) as t2
SET page.page_order = CASE
  WHEN id = :pgid THEN -1
  WHEN page.category_id = t2.oldcategory
    AND page.page_order > t2.oldorder
    THEN page.page_order-1
  ELSE page.page_order
END
WHERE page.category_id = t2.oldcategory AND page.page_order >= t2.oldorder;

; moving
UPDATE page
  , (SELECT category_id as oldcategory, page_order as oldorder FROM page WHERE id = :pgid) as t2
SET page.page_order = CASE
  WHEN id = :pgid THEN :neworder
  WHEN page.category_id = t2.oldcategory
    AND page.page_order > t2.oldorder
    AND (t2.oldcategory != :newcategory OR page.page_order <= :neworder)
    THEN page.page_order-1
  WHEN page.category_id = :newcategory
    AND page.page_order >= :neworder
    AND (t2.oldcategory != :newcategory OR page.page_order < t2.oldorder)
    THEN page.page_order+1
  ELSE page.page_order
END
, page.category_id = CASE
  WHEN id = :pgid THEN :newcategory
  ELSE page.category_id
END
WHERE (t2.oldcategory = :newcategory
    AND page.category_id = :newcategory
    AND page.page_order >= LEAST(:neworder, t2.oldorder)
    AND page.page_order <= GREATEST(:neworder, t2.oldorder))
  OR (t2.oldcategory != :newcategory
    AND ((page.category_id = t2.oldcategory AND page.page_order >= t2.oldorder)
      OR (page.category_id = :newcategory AND page.page_order >= :neworder)));