如果在PHP中存在重复项时,如何只显示一次MySQL数据库记录？

$sql = "SELECT * FROM table_name";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        echo "ID: " . $row['id'] . "<br>";
        echo "Name: " . $row['name'] . "<br>";
        echo "Description: " . $row['description'] . "<br><br>";
    }
}

$sql = "SELECT * FROM table_name";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    $rows = array();
    while($row = mysqli_fetch_assoc($result)) {
        $rows[] = $row;
    }
    echo json_encode($rows);
}