How to show one image instead of four images - php

Question

In Mysql database I have column name "product_id" and there is while statement code to check if row exist ...
If value of product_id exist, then it will show "note-icon.png" image, if not exit it will say "No" but the problem is that let say that in "product_id" has four product_id's SAME NUMBER and then result will SHOW FOUR images, my question is that how to write code to show ONE image instead of FOUR images!
<?php
$sql = new mysqli($mysql_hostname, $mysql_user, $mysql_password, $mysql_database);
$query = "SELECT * FROM notes WHERE product_id = $product_id";
$results = mysqli_query($sql, $query);
while ($row = mysqli_fetch_array($results, MYSQLI_ASSOC)){
if(isset($row['$product_id'])) {
echo "<p>No </p>";
} else {
echo '<img src="images/note-icon.png" width="16" height="16" />';
} }
?>

Answer 1

Select only one row:
MySQL:
SELECT * FROM notes WHERE product_id = ? LIMIT 1
SQL:
SELECT FIRST 1 * FROM notes WHERE product_id = ?
If you want to get all notes but draw one image per product you can do this:
$product_ids = array();
while ($row = mysqli_fetch_array($results, MYSQLI_ASSOC)){
if(!isset($row['product_id'])) {
echo "<p>No </p>";
} else {
if(!isset($product_ids[$row['product_id']])) {
$product_ids[$row['product_id']] = 1;
echo '<img src="images/note-icon.png" width="16" height="16" />';
}
}
}
Some code annotations:
$product_id in your query allowed, only if you are cast it to int before
else use placeholders (prepared statements)
if(isset($row['$product_id']))
What's this? think should be:
if(!isset($row['product_id']))
also you forgot to check $results, that it is not false, before using..

Answer 2

U can use grouping
SELECT * FROM notes WHERE product_id = ? GROUP BY product_id