从一个表中查找并提取数据并将其插入到 php 和 mysql 中的另一个表中

Question

I am creating a sales system and I want to know the cost of a product through its code / id. The part of uploading all the data of a product is fine, but I want to know the cost and that cost to introduce it to another table.

THIS IS IN THE PRODUCT TABLE:

CODE         NAME         COST   PRICE
44730        doritos        1    2
447390       ice            4    6

As an example I want to know what is the cost of the product with the code 44730, for that I have to use the following:

$db = mysqli_connect("localhost", "root", "", "db_midatabase");

$cost = mysqli_query($db, "
SELECT cost FROM product WHERE code=44730
");

Now that same data that in theory should be 1 I want to introduce it in another table that should do this:

$sql = "
INSERT INTO myothertable (cost) VALUES ('$cost')";
mysqli_query($db, $sql);

and there is my mistake and it is that simply if you add something to the database but the data is 0, someone who helps me solve this problem please I would appreciate it

Answer 1

You could use a single INSERT/SELECT query

INSERT INTO myothertable (cost) 
SELECT cost FROM product 
WHERE code=44730