Update record if parameter has a value - SQL, PHP - php

Question

My current code updates all values, and if there is an empty parameter it updates the corresponding field on the table to null. I want to update only the fields that have a value.
This is my code:
$sql = "
UPDATE drinks SET
name = :name, // Mojito -> Update it
description = :description, // Lorem ipsum.. -> Update it
glass_id = :glass_id, // NULL -> do not update
video_url = :video_url // NULL -> do not update
WHERE id = '$drinkId'
";
try {
$db = new db();
$db = $db->connect();
$stmt = $db->prepare($sql);
$stmt->bindParam(':name', $drinkName);
$stmt->bindParam(':description', $description);
$stmt->bindParam(':glass_id', $glassId);
$stmt->bindParam(':video_url', $videoUrl);
$stmt->execute();
// Close databse
$db = null;
} catch(PDOException $e) {
echo $e;
}

Answer 1

you don't want to update those 2 fields when they are empty.
this code check if a field is null and only when it is not null it will add the field to the query, also the same for binding the value.
$sql = 'UPDATE drinks SET';
$sql = sql . 'name = :name,';
$sql = sql . 'description = :description';
if (!is_null($glassId))
$sql = sql . ',glass_id = :glass_id';
if (!is_null($videoUrl))
$sql = sql . ',video_url = :video_url';
$sql = sql . ' WHERE id = :drinkId';
try {
$db = new db();
$db = $db->connect();
$stmt = $db->prepare($sql);
$stmt->bindParam(':name', $drinkName);
$stmt->bindParam(':description', $description);
$stmt->bindParam(':drinkId', $drinkId);
if (!is_null($glassId))
$stmt->bindParam(':glass_id', $glassId);
if (!is_null($videoUrl))
$stmt->bindParam(':video_url', $videoUrl);
$stmt->execute();
// Close databse
$db = null;
} catch(PDOException $e) {
echo $e;
}