Question

I’ve made one table for all comments on a social network site: comment

Also, I’ve one table for all comments assigned to one comment: comment_assign

So, I built a function comment() to implent it easily in each section type (images, userpage, groups, etc). In case of $_GET[‘s’]==user, I want to have wallposts as well as comments on these wallposts. All stored in ‘comment’.

I’ve got this scheme to display this:
1. sql query to get the comments
2. html output
3. another sql query inside this html output to get specified assigned comments of a comment (wallpost in this case)

Now the problem is that my first query displays all comments. Also comments that are supposed to be subcomments. So my question is, if there’s any way to specify in this first query, when I get all my comments, to say: Look in comment_assign if this comment_id is available. And if it is, don’t display this comment, because it’s a subcomment (that I’ll display in mentioned step 3).

Maybe this whole structure may be changed? I would appreciate any suggestions. Even hard to realized ones, but which would be the most efficient.

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Table structure:

comment

id, uid, nid, site, text, date

comment_assign

comment_id, assign_id

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First SQL Query example, which doesnt work to avoid displaying all the comments (also assigned ones). See the last line:

SELECT *    
FROM `comments` AS c
LEFT JOIN `comment_assign` AS ca ON ca.`comment_id` = c.`id` 
LEFT JOIN `users` AS u ON c.`uid` = u.`id` 

WHERE c.`nid`='".$nid."' 
AND c.`site`='".$_GET['s']."' 
AND ca.`comment_id` != c.`id`

Answer 1

If I understand you correctly, you select all the comments from the comment table. You then want to check to see if comment.id is present in comment_assign.comment_id. If it is present, it is a sub-comment. Is that correct?

You can do it two ways – the clean way is to add another field to the comment table and put assign_id there, since each comment can only be associated with another comment, or is a top-level comment (*assign_id is NULL*).

Alternatively, you could LEFT JOIN both tables. Every row where assign_id is NULL, is a wall comment, every row where it has a value means it is assigned as a sub-comment. i.e.

SELECT id, uid, site, text, date
FROM comment
LEFT JOIN comment_assign ON (comment.id = comment_assign.comment_id)
WHERE comment_assign.assign_id IS NULL;