Use Results From One Sql Query In Another Where Statement (subquery?)

I see many similar questions but they're either so complex I can't understand them, or they don't seem to be asking the same thing. It's simple: I have two columns: users (dmid) an

Solution 1:

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

or using a self join

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

if this takes too long then you will probably need to post an explain plan (google it!)