DELETE & INSERT or UPDATE best practice in SQL PDO - php

Question

I'm trying to find an answer which is the best practice for following parts of code:
Let's say I have a single action for add and edit products
DELETE & INSERT
$product_id = 1;
$this->db->query("DELETE FROM `product_description` WHERE `product_id` = :product_id");
$this->db->bind(array(":product_id" => $product_id));
$this->db->execute();
$updateset = array(
":product_id" => $product_id,
":name" => $_POST["name"]
);
$this->db->query("INSERT INTO `product_description` SET `product_id` = :product_id, `name` = :name");
$this->db->bind($updateset);
$this->db->execute();
UPDATE or INSERT
$product_id = 1;
$updateset = array(
":name" => $_POST["name"]
":product_id" => $product_id
);
$this->db->query("UPDATE `product_description` SET `name` = :name WHERE `product_id` = :product_id");
$this->db->bind($params);
$this->db->execute();
if(!$this->db->row_count()) {
$this->db->query("INSERT INTO `product_description` SET `product_id` = :product_id, `name` = :name");
$this->db->bind($updateset);
$this->db->execute();
}
so which is better?

Answer 1

Neither option is good.
Problem 1:
They both are susceptible to a race condition. Another concurrent session might insert a row in the brief time between your two SQL statements.
Problem 2:
In the second solution, if the row-count of the UPDATE is zero, there may still be a matching row, because it won't count rows when the update doesn't change the value in the row.
Problem 3:
If you use the first option, and you use foreign keys, it won't work if there are any child rows referencing the row you delete. Either the delete will be blocked because of the child rows, or else you use ON DELETE CASCADE which means you will accidentally delete the child rows.
Better solution:
Define a UNIQUE constraint for product_id. Your usage suggests that this column would be a candidate key (i.e. there can only be one row per product_id).
Then use INSERT...ON DUPLICATE KEY UPDATE.
$updateset = array(
"product_id" => $product_id,
"name" => $_POST["name"]
);
$this->db->query("INSERT INTO `product_description`
SET `product_id` = :product_id, `name` = :name
ON DUPLICATE KEY UPDATE `name` = VALUES(`name`)");
$this->db->bind($updateset);
$this->db->execute();
Tip: Your array doesn't need to prefix the column names with :. That was required in early versions of PDO, but they changed it so this hasn't been a requirement for years.

Answer 2

The question is quite unclear but the second option looks much better.
The main reason is if your schema evolve and you end up with more columns than you already have, the first option will deleted existing data.
The second option on the other hand will make sure that any existing data will be kept in your database.