Gunakan hasil dari satu kueri sql di pernyataan where lainnya (subquery?)

SELECT dfid,count(*) 
from downloads_downloads 
WHERE dmid IN (
    SELECT dmid 
    FROM downloads_downloads 
    where dfid = "7024"
)
group by dfid

atau menggunakan self join

select t1.dfid,count(*)
from downloads_downloads t1
inner join downloads_downloads t2
on t1.dmid = t2.dmid
where t2.dfid = "7024"

jika ini memakan waktu terlalu lama maka Anda mungkin perlu memposting rencana penjelasan (google it!)