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    <p>If this usecase is a common one in your application, just store the root id (id of the root of the tree. this can be the id of the post to which these comments belong). Now when you need to get the whole tree of comments, you just need to do :</p> <pre><code>SELECT * FROM comments WHERE root_id = &lt;root_id&gt; </code></pre> <p>or an equivalent query for your design. If you provide your table definitions, I can help you out with specific queries.</p> <p>Update:</p> <pre><code>$dbh = new PDO($dsn, $user, $password); $sql = "SELECT A.*, GROUP_CONCAT(descendant) as descendants FROM Comments AS A INNER JOIN Paths AS B ON A.id = B.ancestor WHERE A.item = ? GROUP BY A.id"; $stmt = $dbh-&gt;prepare($sql); $stmt-&gt;execute(array($item)); $data = $stmt-&gt;fetchAll(PDO::FETCH_ASSOC); $adjacency_list = array(); $comments = array(); foreach($data as $row) { $comments[$row['id']] = $row; $descendants = explode(',', $row['descendants']); $adjacency_list[$row['id']] = $descendants; } echo '&lt;UL&gt;'; foreach($adjacency_list[$item] as $top_level_comment) { printTree($top_level_comment, $adjacency_list[$top_level_comment]); } echo '&lt;/UL&gt;'; function printTree($node, $descendants) { echo '&lt;LI&gt;'.$node; if(sizeof($descendants) &gt; 0) { echo '&lt;UL&gt;'; foreach($descendants as $descendant) { $d = array(); if(!empty($adjacency_list[$descendant])) $d = $adjacency_list[$descendant]; printTree($descendant, $adjacency_list[$descendant]); } echo '&lt;/UL&gt;'; } echo '&lt;/LI&gt;'; } </code></pre> <p>Nested Set Model, on the other hand, is not a good solution for commenting system because of the high inserts and updates. It is an efficient solution if you your data is rarely updated.</p>
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    1. POClosure Table the best SELECT QUERY
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    1. COI know it. Thank you, but I don´t know how to render the whole tree wchich belongs to any post.
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      1. USFilip Glazar
    2. COOnce you have the adjacency list, it is a simple matter of traversing the tree. Can you provide your table schema?
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    3. COComments [ id, item, author, ip, text, time, host, vote, vote_counter ] - item is id of post which is commented and I want to show all comments for it Paths [ ancestor, descendant, depth ]
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      1. USFilip Glazar
 

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