php - Mysql Query Join Table on the most recent row -

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i have page of categories, worked fine until did join.

the categories display so:

category 1-----------------------0----------0
discussion 1 someone

category 2-----------------------0----------0
discussion 2 someoneelse

now says discussion, need display last discussion posted category based on it's discussion_id. have tried order ... desc sorts category names not discussion names , posted by. 

 $sql = "select *, count(d.cat_id) count           discussions d           left join categories c on (c.cat_id = d.cat_id)           right join soldiers s on (s.uid = d.discussion_poster)           group d.cat_id";  $result = query($sql);     while (($row = mysqli_fetch_assoc($result)) != false) {           $cat_id = $row['cat_id'];     $discussion_id = $row['discussion_id'];    $cat_title = $row['cat_title'];    $discussion_title = $row['discussion_title'];     $discussion_time = $row['discussion_time'];    $count = $row['count'];    $discussion_poster_id = $row['discussion_poster'];    $discussion_poster = $row['soldier']; } 

$sql = " select * categories c inner join (    select max(discussion_id) discussion_id,    count(discussion_id) count,    cat_id       discussions    group    cat_id ) d1 on (c.cat_id = d1.cat_id) inner join discussions d on (d1.discussion_id = d.discussion_id) inner join soldiers s on (s.uid = d.discussion_poster) group d.cat_id";

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