Update one table where record found in another table - php

Question

I am really struggling on how to achieve this and hope that someone can help me. I have the existing function and query:
public function setStockAndPrice($product_id) {
$query = $this->db->query('UPDATE ' . DB_PREFIX . 'product SET quantity = 0, price = 0.00 WHERE product_id = ' . (int)$product_id)
}
This works, but it sets all products to Zero when I actually want it to only set products to Zero when that product exists in another table.
i.e., in explanatory terms:
public function setStockAndPrice($product_id) {
$query = $this->db->query('UPDATE ' . DB_PREFIX . 'product SET quantity = 0, price = 0.00 WHERE product_id = ' . (int)$product_id AND product_id exists in CustomerProducts)
}
I am not au fait with joins, but I am not sure if I even need to use a join here as the query seems more simple than that.
Can anyone point me in the right direction?

Answer 1

public function setStockAndPrice($product_id) {
$query = $this->db->query('UPDATE ' . DB_PREFIX . 'product SET quantity = 0, price = 0.00 WHERE product_id = ' . (int)$product_id ." AND product_id =(select DISTINCT(product_id) from CustomerProducts where product_id= $product_id)" )
}
This may work.

Answer 2

use this will work for you are not assigning db.product and make sure you write query in a string then execute.
And you see you query, by removing comments
public function setStockAndPrice($product_id) {
$query_string = "UPDATE " . DB_PREFIX . ".product SET quantity = '0', price = '0.00' WHERE product_id = '$product_id'";
// echo "Query : " . $query_string;
$query = $this->db->query($query_string);
}

Answer 3

public function setStockAndPrice($product_id) {
$query = $this->db->query('UPDATE ' . DB_PREFIX . '.product p, ' . DB_PREFIX . '.CustomerProducts cp SET p.quantity = 0, p.price = 0.00 WHERE p.product_id = ' . (int)$product_id . ' AND p.product_id = cp.product_id');
}