Update SQL query from post data - mysql

Question

I've script with import csv and column mapping.
After mapping column .csv in html table I need udate data.
I try write this script:
$file_data = $_SESSION['file_data'];
unset($_SESSION['file_data']);
foreach($file_data as $row)
{
$data[] = '("'.$row[$_POST["sku"]].'", "'.$row[$_POST["stock"]].'")';
}
if(isset($data))
{
$query = "
UPDATE products
SET (sku, stock)
VALUES ".implode(",", $data)."
WHERE sku = ".$row[$_POST["sku"]]."
";
$statement = $connect->prepare($query);
if($statement->execute())
{
echo 'Data Updated Successfully';
}
}
But I have problem with construct correct and valid udate query:
$query = "
UPDATE products
SET (sku, stock)
VALUES ".implode(",", $data)."
WHERE sku = ".$row[$_POST["sku"]]."
";
I try also in this way but still something went wrong:
$file_data = $_SESSION['file_data'];
unset($_SESSION['file_data']);
foreach($file_data as $row)
{
$query = "
UPDATE products
SET sku = '.$row[$_POST["sku"]].', stock = '.$row[$_POST["stock"]].'
WHERE sku = '.$row[$_POST["sku"]].'
";
$statement = $connect->prepare($query);
I try also:
$file_data = $_SESSION['file_data'];
unset($_SESSION['file_data']);
foreach($file_data as $row)
{
$data1[] = '("'.$row[$_POST["sku"]].'")';
$data2[] = '("'.$row[$_POST["stock"]].'")';
}
if(isset($data, $data2))
{
$query = "
UPDATE products
SET stock = ".implode(",", $data2)."
WHERE sku = ".implode(",", $data)."
";
$statement = $connect->prepare($query);
if($statement->execute())
{
echo 'Data Updated Successfully';
}
}
I need update values stock with rule where sku = and here post values sku from csv file