When selecting two tables from the database with one query, duplicates are obtained in the output. What could be the problem?

Question

PHP

Hello! When I select two tables from the database, it turns out that I have duplicate products displayed. What I understood is the number of duplicates depends on how many rows there are in the other table.
There is a table `table_products` and `cart` . Each row, when output from the `table_products` table , is output as many times as there are rows in the `cart` table .
Example: `table_products` has 2 rows, NAME_1 and NAME_2 . There are 4 lines in `cart` .
OUTPUT: NAME_1 NAME_1 NAME_1 NAME_1 NAME_2 NAME_2 NAME_2 NAME_2

Here is my query:

$query = $pdo->query("SELECT * FROM table_products, cart");
while ($row = $query->fetch(PDO::FETCH_OBJ)) {
<div class="product" id="<?php echo"$row->products_id"; ?>">
<img src="<?php echo"$row->image"; ?>" class="image-product">
<div class="title-prod"><h2><a href="product.php?id=<?php echo "$row->products_id"; ?>"><?php echo "$row->title"; ?></a></h2></div>
}

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Thank you all! Everyone who answered gave me the right solution to my problem, thank you so much!
PS: My query is now: SELECT * FROM table_products LEFT JOIN cart ON table_products.products_id = cart.cart_id_products

Answer 1

You are sampling the Cartesian product of two tables. So at the output you have all possible pairs of rows from the first and second tables.