Update all rows primary key columnin a table - Joomla 3.4.8

Question

I have a temp table created with a list of "master tasks". These need to be duplicated so they can be assigned to users as needed. The problem I have is the table column 'id' is a primary key set to auto increment...how can I update the id column for all rows within the table to something like ++$nid ($nid is the max from another table so I do not have duplicate id's). Here is the code used to update the ID, but it only works when I lock the table, remove the auto increment and drop the primary key..but then the id's are all 206 (first id should be 187 - 206). Any way to update multiple rows where the column is ai and a primary key?

$db    = JFactory::getDbo();
$query = $db->getQuery(true);
$query->select(array('id'))
    ->from('#__temp_tasks');
$db->setQuery($query);
$rows =$db->loadObjectList();

    foreach ($rows as $row)
{
  // Insert into destination table
  $query->clear();
  $query->update('#__temp_tasks');
  foreach ($row as $rows)
  {
      $query->set('id' . ' = ' . (int) ++$tasksMaxID);

  }
  $db->setQuery($query);
  $db->execute();
  $query->clear();
} 

Answer 1

If I understand you correctly, you should use $query->insert('#__temp_tasks') rather than $query->update('#__temp_tasks'), as you want to insert new rows in the table, is that correct?

I would simplify your task:

// Your first two lines
$db    = JFactory::getDbo();
$query = $db->getQuery(true);
// ...then:
$sql="insert into #__temp_tasks (id, col2, col3) ".
"select id+".$MaxID.", col2, col3 from #__temp_tasks ".
"where id between 0 and 100"; // I guess you need something like this
// ...otherwise your table will grow awfully fast...
$query->setQuery($sql);
// ...your last three lines, more or less
$db->setQuery($query);
$db->execute();
$query->clear();