SELECT DISTINCT A.actor_name, COUNT(1) as articles

FROM ukwiki_p.revision R

 JOIN ukwiki_p.page P1 ON R.rev_page = P1.page_id

 JOIN ukwiki_p.page P2 ON P1.page_title = P2.page_title

 JOIN ukwiki_p.categorylinks CL ON P2.page_id = CL.cl_from

 JOIN ukwiki_p.actor A ON R.rev_actor = A.actor_id

WHERE R.rev_parent_id = 0

 AND P1.page_namespace = 0

 AND P2.page_namespace = 1

 AND P1.page_is_redirect = 0

 AND CL.cl_to LIKE "Статті_конкурсу_«Європейська_весна_2021»%"

 AND R.rev_timestamp >= 20210401000000

 AND R.rev_timestamp < 20210501000000

GROUP BY A.actor_name

ORDER BY articles DESC