select page_title, substr(iwl_title, 10)

from hewiki_p.iwlinks 

inner join hewiki_p.page p

on p.page_id=iwl_from 

where 

    iwl_prefix='commons' and length(iwl_title)>0 

    and iwl_title like 'Category:%' and p.page_namespace =0 

    and not exists(select * from commonswiki_p.page cp 

                   where cp.page_title=substr(iwl_title, 10) 

                   and cp.page_namespace=14)

limit 1000;