Ok, I would like to use a CASE STATEMENT for this, but I am lost with this. Basically, I need to update a ton of rows, but just on the "position" column. I need to update all "position" values from 0 - count(position) for each id_layout_position column per id_layout column.

Here's what I got for a regular update, but I don't wanna throw this into a foreach loop, as it would take forever to do it. I'm using SMF (Simple Machines Forums), so it might look a little different, but the idea is the same, and CASE statements are supported...

    $smcFunc['db_query']('', '
            UPDATE {db_prefix}dp_positions
            SET
                position = {int:position}
            WHERE id_layout_position = {int:id_layout_position} AND id_layout = {int:id_layout}',
            array(
                'position' => $position++,
                'id_layout_position' => (int) $id_layout_position,
                'id_layout' => (int) $id_layout,
            )
        );

Anyways, I need to apply some sort of CASE on this so that I can auto-increment by 1 all values that it finds and update to the next possible value. I know I'm doing this wrong, even in this QUERY. But I'm totally lost when it comes to CASES. Here's an example of a CASE being used within SMF, so you can see this and hopefully relate:

$conditions = '';
        foreach ($postgroups as $id => $min_posts)
        {
            $conditions .= '
                    WHEN posts >= ' . $min_posts . (!empty($lastMin) ? ' AND posts <= ' . $lastMin : '') . ' THEN ' . $id;
            $lastMin = $min_posts;
        }

        // A big fat CASE WHEN... END is faster than a zillion UPDATE's ;).
        $smcFunc['db_query']('', '
            UPDATE {db_prefix}members
            SET id_post_group = CASE ' . $conditions . '
                    ELSE 0
                END' . ($parameter1 != null ? '
            WHERE ' . (is_array($parameter1) ? 'id_member IN ({array_int:members})' : 'id_member = {int:members}') : ''),
            array(
                'members' => $parameter1,
            )
        );

Before I do the update, I actually have a SELECT which throws everything I need into arrays like so:

$disabled_sections = array();
    $positions = array();
    while ($row = $smcFunc['db_fetch_assoc']($request))
    {
        if (!isset($disabled_sections[$row['id_group']][$row['id_layout']]))        
            $disabled_sections[$row['id_group']][$row['id_layout']] = array(
                'info' => $module_info[$name],
                'id_layout_position' => $row['id_layout_position']
            );

        // Increment the positions...
        if (!is_null($row['position']))
        {
            if (!isset($positions[$row['id_layout']][$row['id_layout_position']]))
                $positions[$row['id_layout']][$row['id_layout_position']] = 1;
            else
                $positions[$row['id_layout']][$row['id_layout_position']]++;
        }
        else
            $positions[$row['id_layout']][$row['id_layout_position']] = 0;
    }

Thanks, I know if anyone can help me here it's definitely you guys and gals...

Anyways, here is my question:

How do I use a CASE statement in the first code example, so that I can update all of the rows in the position column from 0 - total # of rows found, that have that id_layout value and that id_layout_position value, and continue this for all different id_layout values in that table?

Can I use the arrays above somehow? I'm sure I'll have to use the id_layout and id_layout_position values for this right? But how can I do this?