根据每个ID的自定义公式，仅用1个输入字段来更改MySQL价格？

Question

I have a database with some prices in it:

But I want that I can give every id a formula like : [thatnumber] * or / or - or + . = [AndShowThatPrice]

So for a example: I want just to type here a price:

If I type 10 then I want that the formula for the id=0 will be like: 10 * 8 = 80 <<--- Update to that price in MySQL

And so I want to give each id a formula So for id=1 example: 10 + 140 = 150 <<--- Update to that price in MySQL

* I just want to type the total price in one field, like : 10, then from that value the math will be made and the total price will updated in the database *

Answer 1

You would need at least one other field on the table that would contain your math for prices. For instance a field called math that would be +140. The you could do an update statement with one input box

Answer 2

You can use a CASE statement in your update clause based on the id. It looks something like this:

UPDATE myTable
SET price = 
   CASE WHEN id = 0 THEN (10 * 8)
   WHEN id = 1 THEN (10 + 140) ELSE
   0 END;

You will have to determine a business rule to fall back on if the id isn't in any of your categories. In my example, I just set it to 0.

Answer 3

One possible solution could be: You have four possible operations and you can say that each operation
have one id number, eg: 0 for +, 1 for -, 2 for * and 3 for / then use the module operator to determine which operator use, something like:

For example if you're using PDO.

... get the PDO conn

try {
    $conn = new PDO('mysql:host=localhost;dbname=myDatabase',      $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);    

    $stmt = $conn->prepare('SELECT * FROM myTable');
    $stmt->execute();

    while($row = $stmt->fetch()) {
        print_r($row);
        $operator = $row['id'] % 4;
        switch ($operator) {
            case 0:
                $newValue = $inputField + price;
                break;
            case 1:
                $newValue = $inputField - price;
                break;
            case 2:
                $newValue = $inputField * price;
                break;
            default:
                $newValue = $inputField / price;
       }
       $updateStmt = $conn->prepare('UPDATE myTable set prijs = :pirjs WHERE id = :id');
       $updateStmt->execute(array('prijs' = $newValue, 'id' => $row['id']));$stmt->execute(array('id' => $id));
    }
} catch(PDOException $e) {
    echo 'ERROR: ' . $e->getMessage();
}