SQL 我如何根据在数组中找到的值使用准备好的语句连接两个表

Question

I have the table products which contains the following:

product_id | name | category | img
1            car     toy        tcar.jpg
2            boat    toy        tboat.jpg
3            plane   actual     plane.jpg

I also have the table product which contains the following:

product_id | size | price 
1            large   5
2            small   3
2            medium  4
3            small   7

Finally, I have a multidimensional array called $products_in_cart, with key equal to product_id. It stores the following values:

Array ( [1] => Array ( [Quantity] => 1 [Size] => large) [2] => Array ( [Quantity] => 5 [Size] => medium ) )

I want to inner join products and product and then fetch the products which are found in the array $products_in_cart. (so I will fetch based on the product_id (the keys in $products_in_cart) as well as the size). This has to be done using prepared statements.

I managed to fetch products which are found in $products_in_cart using these statements:

$array_to_question_marks = implode(',', array_fill(0, count($products_in_cart), '?'));
$stmt = $pdo->prepare('SELECT * FROM products WHERE product_id IN (' . $array_to_question_marks . ')');
$stmt->execute(array_keys($products_in_cart));
$products = $stmt->fetchAll(PDO::FETCH_ASSOC);

This gives the output:

Array ( [0] => Array ( [product_id] => 1 [name] => car [category] => toy [img] => tcar.jpg) [1] => Array ( [product_id] => 2 [name] => boat [category] => toy [img] => tboat.jpg))

However, what I want is to get this output:

Array ( [0] => Array ( [product_id] => 1 [name] => car [category] => toy [img] => tcar.jpg [size] => large [price] => 5) [1] => Array ( [product_id] => 2 [name] => boat [category] => toy [img] => tboat.jpg [size] => medium [price] => 4))

I expect that I should inner join products and product and then pick those with id's and size that match the ones in $products_in_cart. However I got no clue on how to do that (prepared statements are making the process complicated for me).

I'm sorry for my poor description of the problem, but I hope that the example of what I managed to do makes it clear , thanks!

Answer 1

Well, if you want to do a inner join, just... do an inner join. Nothing says you can't do one within a prepared statement!

Replace this line

$stmt = $pdo->prepare('SELECT * FROM products WHERE product_id IN (' . $array_to_question_marks . ')');

With this one (I'm spliting it in lines for better clarity):

$stmt = $pdo->prepare('SELECT * FROM products 
            INNER JOIN product 
            ON (products.product_id = product.product_id) 
            WHERE products.product_id IN (' . $array_to_question_marks . ')');

You could also use the "shorthand" version if you prefer:

$stmt = $pdo->prepare('SELECT * FROM products, product 
            WHERE products.product_id = product.product_id 
            AND products.product_id IN (' . $array_to_question_marks . ')');

As a side note, using two similar named tables is confusing. Since the "product" table contains sizes and prices and no product information, you could rename it to something like "prices_sizes" or something like that.