如何从查询到字段的一条记录中获取单个值

Question

In my system, I have plenty of instances of code like the following:

$value = mysqli_fetch_array(mysqli_query($con, "SELECT SUM(price) as total from items WHERE a=1 AND b=2"));

Then $value is used later in the code and has the total price calculated from the array

I'm trying to replicate this in a new piece of code as follows:

$recent_sale_id = mysqli_fetch_array(mysqli_query($con, "SELECT id as id FROM items where item_code='$item_code' and status='BULK-ITEM-SALE' order by sold_at DESC LIMIT 1"));

The query works when run directly against the database (of course replacing $item_code with the item code). But $recent_sale_id then just has the value 'Array'.

I'm wondering two things:

1. What am I doing wrong? My code seems to be exactly the same as the other code that works correctly.

2. Is there a simpler way to get a value from a query into a field, without using a function that seems like it will create an array? Is there a more suitable mysqli_fetch* function?

Answer 1

There's no way you could access $value as a number because it is also an array. In the first case you would need to use either $value[0] or $value['total'] to get the result; in the second either $recent_sale_id[0] or $recent_sale_id['id'] . You can use either form because mysqli_fetch_array by default returns arrays indexed both by column number and column name.

Unfortunately the MySQLi interface does not have an equivalent to PDO's fetchColumn which allows you to directly fetch the value of a single column from a row in a result set.

Answer 2

If $recent_sale_id is returning a array in this case, that means it is of array type and in terms of getting data from mysql query often it comes in array format though you have added a limit 1.

One thing you can do to get the value is try $recent_sale_id[0] for the actual output.