<?php
    $servername = "localhost";
    $username = "username";
    $password = "";
    $dbname = "dbname";

   // Create connection
   $conn = new mysqli($servername, $username, $password, $dbname);
  // Check connection
   if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
   }

   $sql = "SELECT comment_txt, name, comment_date FROM mytablename where productcomment_increment_id='$productId' && comment_status='Approved'";
   $result = $conn->query($sql);

   if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "<i><b>Author Name:</b></i>";
        echo $row["name"];
        echo "<br /><i><b> Comment: </i></b>";
        echo $row["comment_txt"];
        echo "<br /><i><b>Date: </i></b>";
        echo $row["comment_date"];
        echo "<br><br>";
    }
   } else {
   //echo "0 results";
   }
   $conn->close();
   ?>

//database read adapter

$read = Mage::getSingleton('core/resource')->getConnection('core_read');

$results = $read->fetchAll("select * from your_tablename");
foreach($results as $row)
{
    echo "<i><b>Author Name:</b></i>";
    echo $row["name"];
    echo "<br /><i><b> Comment: </i></b>";
    echo $row["comment_txt"];
    echo "<br /><i><b>Date: </i></b>";
    echo $row["comment_date"];
    echo "<br><br>";
}