Question

I’m having a problem with the order of my query with a group by.

I have a table download_category and download. The download table has a column named “thumb” (it’s a image – varchar). I want to get name of category and the last thumb inserted.

I’m doing this way:

    SELECT download_category.id
             , download_category.link
             , download.thumb
      FROM download  

RIGHT JOIN download_category ON (download_category.id = download.idCategoria )   
     WHERE download_category.link IN ('link-of-category') 

GROUP BY download_category.id
       , download_category.link
ORDER BY download.id DESC 

The RIGHT JOIN is necessary in case of not exists a download.

The problem is: the thumb columns is returning the first inserted record, instead the last “download.id DESC”. What am I doing wrong?

Answer 1

Try this:

SELECT download_category.id
         , download_category.link
         , download.thumb
from download_category 
left join (select max(id) maxId,
                  idCategoria 
           from download 
           group by idCategoria) t
      ON (download_category.id = t.idCategoria ) 
left join download 
      ON t.maxid=download.id

 WHERE download_category.link IN ('link-of-category') 

 GROUP BY download_category.id
        , download_category.link
 order by t.maxid DESC;