如何从MySQL数据库检索行和列的特定组合？

Question

I have a database which has an INT column called "registries", and a method that updates this column registries. But first I need to retrieve the data from the specific row/column combination. I was trying to do this in this way:

$result = mysqli_query($link,"SELECT registries FROM product WHERE name = '".$update."'");

Then, the new update variable is, let's say:

$update = $result + 5;

But it doesn't work. Please, can anybody help me?

Answer 1

The mysqli_query function do not return an integer, returns an object for fetching data.

http://www.php.net/manual/en/mysqli.query.php says:

For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object

You have to do this:

$resource = mysqli_query($link,"SELECT registries FROM product WHERE name = '".$update."'");
$result = $resource->fetch_object()->registries;
$update = $result + 5;

Answer 2

使用一个查询更新它：

UPDATE products SET registries = registries + 5 WHERE name = '$update'