how to get wordpress post with by category with images

[admin]

I have installed wordpress and opencart in same database. Trying to get wordpress posts table inside opencart module. got the mysql query to fetch all information except image. I dont why images are different from the post in loop of result. Kindly guide, following is the code.

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "tablename";
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {die("Connection failed: " . $conn->connect_error);}
$sql = "SELECT * FROM wp_posts WHERE post_type = 'attachment' ORDER BY ID DESC LIMIT 3";
$result = $conn->query($sql);
if ($result->num_rows > 0) {

while($row = $result->fetch_assoc()) {
echo '<div class="col-sm-4">';
echo "Post ID: " . $row["ID"] . " / ";
echo "Post Title: " . $row["post_title"] . " / ";
echo "Post Title: " . $row["post_date"] . " / ";
echo '<img src="' . $row['guid'] . '" class="img-responsive">';
echo '</div>';
}
} else {
echo "0 results";
}