MySQL query for hierarchical table structure - php

Question

I am trying to build a comment system below my articles where users can reply on the comment as well. Comment or its reply can be posted by only logged-in users.
There I have created 4 tables in MySQL.
User Table
<style type="text/css">
table.tableizer-table {
border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
}
.tableizer-table td {
padding: 4px;
margin: 3px;
border: 1px solid #ccc;
}
.tableizer-table th {
background-color: #104E8B;
color: #FFF;
font-weight: bold;
}
</style>
<table class="tableizer-table">
<tr class="tableizer-firstrow"><th>id</th><th>email</th></tr>
<tr><td>1</td><td>abc#gmail.com</td></tr>
<tr><td>2</td><td>xyz#gmail.com</td></tr>
<tr><td>3</td><td>pqr#gmail.com</td></tr>
<tr><td>4</td><td>abc#yahoo.com</td></tr>
<tr><td>5</td><td>xyx#yahoo.com</td></tr>
</table>
Profile Table
<style type="text/css">
table.tableizer-table {
border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
}
.tableizer-table td {
padding: 4px;
margin: 3px;
border: 1px solid #ccc;
}
.tableizer-table th {
background-color: #104E8B;
color: #FFF;
font-weight: bold;
}
</style>
<table class="tableizer-table">
<tr class="tableizer-firstrow"><th>id</th><th>user_id</th><th>fname</th><th>lname</th></tr>
<tr><td>1</td><td>3</td><td>PQR</td><td>Gmail</td></tr>
<tr><td>2</td><td>2</td><td>XYZ</td><td>Gmail</td></tr>
<tr><td>3</td><td>1</td><td>ABC</td><td>Gmail</td></tr>
<tr><td>4</td><td>5</td><td>XYZ</td><td>Yahoo</td></tr>
<tr><td>5</td><td>4</td><td>ABC</td><td>Yahoo</td></tr>
</table>
Article Table
<style type="text/css">
table.tableizer-table {
border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
}
.tableizer-table td {
padding: 4px;
margin: 3px;
border: 1px solid #ccc;
}
.tableizer-table th {
background-color: #104E8B;
color: #FFF;
font-weight: bold;
}
</style>
<table class="tableizer-table">
<tr class="tableizer-firstrow"><th>id</th><th>article_title</th><th>article_content</th></tr>
<tr><td>1</td><td>Helooooooo</td><td>Hi, How are you?</td></tr>
<tr><td>2</td><td>Hiiiiiiiiiiii</td><td>Hey, How are you?</td></tr>
<tr><td>3</td><td>Heeeeeey</td><td>Hello, How are you?</td></tr>
</table>
Comment Table
<style type="text/css">
table.tableizer-table {
border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
}
.tableizer-table td {
padding: 4px;
margin: 3px;
border: 1px solid #ccc;
}
.tableizer-table th {
background-color: #104E8B;
color: #FFF;
font-weight: bold;
}
</style>
<table class="tableizer-table">
<tr class="tableizer-firstrow"><th>id</th><th>article_id</th><th>user_id</th><th>parent_comment_id</th><th>Comment</th></tr>
<tr><td>1</td><td>2</td><td>5</td><td>0</td><td>Great Article</td></tr>
<tr><td>2</td><td>2</td><td>2</td><td>0</td><td>Nice Article</td></tr>
<tr><td>3</td><td>2</td><td>4</td><td>1</td><td>I agree Great Article</td></tr>
<tr><td>4</td><td>2</td><td>1</td><td>1</td><td>I also agree Great Article</td></tr>
<tr><td>5</td><td>2</td><td>3</td><td>0</td><td>Bad Article</td></tr>
<tr><td>6</td><td>2</td><td>4</td><td>2</td><td>OK Artilce</td></tr>
</table>
I want my output to display as:
Name: XYZ Yahoo (Comment)
Great Article
Name: ABC Yahoo (Reply on 1st Comment)
I agree Great Article
Name: ABC Gmail (Reply on 1st Comment)
I also agree Great Article
Name: XYZ Gmail (Comment)
Nice Article
Name: ABC Yahoo (Reply on 2nd Comment)
OK Artilce
Name: PQR Gmail (Comment)
Bad Article
In the above comment system i am using hierarchical table structure to store comment and its replys.
Hope i have been able to explain my problem.
Can someone help me with MySQL statement and php code

Answer 1

I would tweak the order by clause a little bit so you would get all posts in the right order on php side, so you can simply loop through the resultset.
$sql = 'SELECT c.id, parent_comment_id,`comment`, p.fname, p.lname FROM comment c INNER JOIN profile p on c.user_id=p.user_id INNER JOIN WHERE article_id='.$article_id . ' ORDER BY IF(parent_comment_id=0,id,parent_comment_id) ASC, id ASC;'
While looping through the resulset in php I would build an array to hold the ids of each record to determine their rank within the comments. Although, I should note, that on forums you can rarely see the reference that a comment is a response to the first comment, you can usually see that a comment is a response to a comment made by sy at such and such time. Anyway, the helper array can hold user names and timestamps of the records as well.
//outside the loop
//initialise rowcount variable to 0
$rowcount=0
...
//within the loop
//rowcount variable
$rowcount++;
$helper[$row['id']]=$rowcount;
...
//if a comment has a parent comment, get the parent's rownumber
echo 'Reply to ' . $helper[$row['parent_comment_id']] . '. comment';