Question

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 that are great than the position value that was removed to position - 1 on a per id_layout and id_layout_position basis.

OK, here is a pic of what the table looks like:
alt text http://acs.graphicsmayhem.com/images/dp_positions_table.png

Now let’s say I delete the circled row, this will remove position = 2 and give me: 0, 1, 3, 5, 6, 7, and 4. It should reposition the position values that are greater than 2, so that it looks like this: 0, 1, 2, 4, 5, 6, and 3.

OK, Here’s what I got so far within the DELETING of the ROW, so here’s how it looks for this (NOTE: $module_info[‘clones’] = an array of clones to delete, in the table above there would be none, because all id_clone values are 0, and $module_info[‘id’] is the id_module value that we are removing):

// Get rid of id_clone = 0, because we can't use them.
$module_info['clones'] = array_values(array_filter($module_info['clones']));

// Selecting the positions.
if (isset($module_info['clones'][0]))
    $query = 'id_module = {int:id_module} || id_clone IN ({array_int:id_clones})';
else
    $query = 'id_module = {int:id_module}';

$request = $smcFunc['db_query']('', '
    SELECT
        id_position, id_layout_position, id_layout, position
    FROM {db_prefix}dp_module_positions
    WHERE ' . $query,
    array(
        'zero' => 0,
        'id_module' => $module_info['id'],
        'id_clones' => $module_info['clones'],          
    )
);

while ($row = $smcFunc['db_fetch_assoc']($request))
{
    $module_info['position'][$row['id_layout']]['pos' . $row['id_position'] . $row['position'] . '_' . $row['id_layout_position']] = $row['position'];
    $module_info['id_positions'][] = $row['id_position'];
}

$smcFunc['db_free_result']($request);

// Remove all module and clone positions from the layout!
$smcFunc['db_query']('', '
    DELETE FROM {db_prefix}dp_module_positions
    WHERE id_position IN ({array_int:id_positions})',
    array(
        'id_positions' => $module_info['id_positions'],
    )
);

foreach($module_info['position'] as $id_layout => $id_layout_pos)
{
    foreach($id_layout_pos as $key => $position_val)
    {
        $lPos = explode('_', $key);
        $lPosId = (int) $lPos[1];

        $smcFunc['db_query']('', '
            UPDATE {db_prefix}dp_module_positions
            SET
                position = position - 1
            WHERE position > {int:position} AND id_layout = {int:id_layout} AND id_layout_position = {int:id_layout_position}',
            array(
                'id_layout' => (int) $id_layout,
                'position' => (int) $position_val,
                'id_layout_position' => $lPosId,
            )
        );
    }
}

NEW QUESTION:
THERE’s Just gotta be some sort of way to use a CASE STATEMENT in this UPDATE now. For Example, I now need to update all positions to position – 1, on a per id_layout, and per id_layout_position basis. BUT only where the position is greater than the current position for that id_layout and id_layout_position value.

Is there anyway to do this without using a FOREACH LOOP?

Answer 1

Before you delete a row, you could get it’s position and decrement the position of all rows which have a higher position.

Pseudo code :

function deleteRow($id){
  DB::startTransaction()
  try{
    $infos = DB::getData('SELECT position FROM db_positions WHERE id_position = :ID', array(':ID' => $id));
    if(empty($infos)){
      throw("useless ID");
    }
    DB::query('DELETE FROM db_positions WHERE id_position = :ID', array(':ID' => $id));
    DB::query('UPDATE db_positions SET position = position - 1 WHERE position > :position', array(':position' => $infos['position']);
    DB::commit();
  }
  catch(Exception $e){
    DB::rollBack();
  }
}