SQL Query for Updating Rows with New Values from Temporary Table in Laravel/Eloquent - laravel

Question

I wish to update table B based on source table A so that if a new record is found, we can insert it otherwise update the record if any values have changed. How would I write the query in laravel 4 using eloquent?
Table A Table B
======= =======
Name | Color Name | Color
---------------------- ----------------------
Mickey Mouse | grey Mickey Mouse | red
Donald Duck2 | green Donald Duck | blue
Donald Duck | blue Minnie | red
Goofy | black
Minnie | red
In this example table B should be inserted with the rows Goofy and Donald Duck2 and the row mickey mouse should be updated with the new color grey.

Answer 1

This should work:
$a = A::all();
foreach($a as $current)
{
$b = B::where("name", "=", $current->name)->first();
if(!$b) $b = new B;
if($b->name != $current->name)
{
$b->name = $current->name;
$b->save();
}
}
Or more optimized:
$a = A::all();
// using this script: http://stackoverflow.com/questions/12050892/array-mapping-in-php-w ith-keys
$aFolded = array_reduce($a, function(&$result, $item){
$result[$item->name] = $item->color;
return $result;
}, array());
// so we now have array ( name => color, name2 => color2 )
$b = B::with("a", "name")->get(); // might recheck with laravel doc
foreach($b as $updateMe)
{
if($updateMe->color != $aFolded[$b->name])
{
$updateMe->color = $aFolded[$b->name];
$updateMe->save();
unset($aFolded[$b->name]);
}
}
// after this $aFolded will only contain the names which do not exist in b so we can just insert them all (maybe the insert query could be better)
foreach($aFolded as $name => $color)
{
DB::table("B")->insert(array("name" => $name, "color" => $color));
}