php - Retrieve latest topic of subcategory -

i trying retrieve latest topic of subcategory. here sql:

    select * threads left join subs  on subs.category_id = threads.subcategory_id left join categories  on categories.id = subs.category_id inner join (     select id, max(lastdate) lastdate     threads     group id ) b on subs.category_id = threads.subcategory_id , threads.lastdate = b.lastdate group subs.category_id, threads.subcategory_id, threads.lastdate desc 

however, if trying make thread subcategory links category used twice, doesn't work.

maybe can me out.

subs in database: (as can see, of subcategories has same category_id

updated query. duplicate echo output each new category linked category used twice: http://joxi.ru/dmbjzq5c1ll0mp