USE dewiki_p;
/* Info: the category page 'See_in_den_Vestfoldbergen' (namespace 14) is a subcategory page of 'Vestfoldberge' (namespace 14) */
SELECT page_namespace FROM page WHERE page_title = 'See_in_den_Vestfoldbergen';
/* gives --> 14 */
SELECT cat_subcats FROM category WHERE cat_title = 'Vestfoldberge';
/* gives --> 0 */
/* !!! How can that give 0, if 'See_in_den_Vestfoldbergen' is a subcat of 'Vestfoldberge'? !!! */

• See https://de.wikipedia.org/w/index.php?title=Kategorie:See_in_den_Vestfoldbergen&action=info || Category page See_in_den_Vestfoldbergen has been is namespace "Category" == 14
• See https://de.wikipedia.org/w/index.php?title=Kategorie:Vestfoldberge&action=info || Category page Vestfoldberge, what should be the supercategory page of See_in_den_Vestfoldbergen, counts 89 pages as category member, but there are only 88 members and one subcategory, that is not counted. This is comparable to the result of the SQL Query mentioned above too.

My question is, why are there two different results in both the database tables 'page' and 'category'.

There are some more erroneous pairs in dewiki_p:

1. https://de.wikipedia.org/w/index.php?title=Kategorie:Katsushika&action=info has 1 subcategory but SELECT cat_subcats gives 0.
2. https://de.wikipedia.org/w/index.php?title=Kategorie:Norton_County&action=info has 1 subcategory but SELECT cat_subcats gives 0.
3. https://de.wikipedia.org/w/index.php?title=Kategorie:Erfrischungsgetränk&action=info has 1 subcategory but SELECT cat_subcats gives 0.
4. https://de.wikipedia.org/w/index.php?title=Kategorie:FIA-Langstrecken-Weltmeisterschaft_2018/19&action=info has 1 subcategory but SELECT cat_subcats gives 0.
5. https://de.wikipedia.org/w/index.php?title=Kategorie:Organisation_(Benton_County,_Washington)&action=info has 1 subcategory but SELECT cat_subcats gives 0.
6. https://de.wikipedia.org/w/index.php?title=Kategorie:Organisation_(Christchurch)&action=info has 1 subcategory but SELECT cat_subcats gives 0.
7. https://de.wikipedia.org/w/index.php?title=Kategorie:Person_(Tyler,_Texas)&action=info has 1 subcategory but SELECT cat_subcats gives 0.

... and some more