USE enwiki_p;

​

SELECT count(*) AS numredirs_wpmed

FROM categorylinks cl1

JOIN page tp1

ON (tp1.page_id=cl1.cl_from)

JOIN page art1

ON (tp1.page_title=art1.page_title

    AND art1.page_namespace=0)

JOIN redirect

ON (art1.page_namespace=rd_namespace

    AND art1.page_title=rd_title)

JOIN page art2

ON (art2.page_id=rd_from)

JOIN page tp2

ON (art2.page_title=tp2.page_title

    AND tp2.page_namespace=1)

JOIN categorylinks cl2

ON (tp2.page_id=cl2.cl_from)

WHERE cl1.cl_to="All_WikiProject_Medicine_articles"

AND cl2.cl_to="All_WikiProject_Medicine_articles"

AND tp1.page_namespace=1

AND art2.page_namespace=0;