如何在SQL中获取另一列等于值的一列中的值，并存储到PHP数组中？

Question

Here is my table:

user_id | group_id
------------------
1       | 22
2       | 22
3       | 22
4       | 1
5       | 1

I only want to get the user_id's from the group_id 22 and store them into an array.

My code in PHP:

$group_id=22;
$user_ids_ar = mysqli_fetch_array($db->query("SELECT user_id FROM table WHERE group_id=".$group_id.";"), MYSQLI_NUM);

It only seems to return one value instead of the expected 3. How can I solve this?

Answer 1

You are only getting one row returned because you are only asking for one row. You need to loop over the fetch to get them all.

$group_id=22;
$result = $db->query("SELECT user_id FROM table WHERE group_id=".$group_id);
while ( $row = mysqli_fetch_array($result, MYSQLI_NUM) ) {
    $user_ids_ar[] = $row;
}

Or you could use fetchAll in the form you were using.

$group_id=22;
$user_ids_ar = mysqli_fetch_all(
                                $db->query("SELECT user_id 
                                            FROM table 
                                            WHERE group_id=".$group_id)
                            , MYSQLI_NUM);