SELECT in UPDATE in the same table - php

Question

my MYSQL Database looks like this:
short -- idnumber--position
abc.......8765...........4
def........7453...........1
abc.......7398...........5
def........7542...........2
I have the idnumber and want to Update all with the the same 'short' as the idnumber. Update should be Position-1.
i have idnumber: 8765 its position should be 3 and position of id 7398 should be 4
How do i do it correctly? My Code dont work and i got no echo
<?php
$pdo = new PDO('mysql:host=localhost;dbname=testdb1', 'root', '');
$idV = $_GET['id'];
$statement = $pdo->prepare("UPDATE idtabelle SET position = position-1 WHERE short IN
(SELECT short FROM idtabelle WHERE idnumber = :idV)");
$statement->bindParam(':idV', $idV);
$statement->execute();
while ($row = $statement->fetch(PDO::FETCH_ASSOC))
{
echo $row['short'];
};
?>

Answer 1

try this. you can give a start id.
UPDATE idtabelle
SET position = position -1
WHERE idnumber = 8765
AND position > 2
ORDER BY position ASC;

Answer 2

You're attempting to fetch a row result from an UPDATE statement which doesn't return rows. (Your SELECT subquery is returning it's rows only to the UPDATE query -- the UPDATE result is the only thing returned to you.)
What you should be doing is something like:
...
$statement->bindParam(':idV', $idV);
if ($statement->execute())
echo $statement->rowCount() . " rows updated";
else
echo "Update failed with error: " .print_r($statement->errorInfo(), TRUE);
...
If you need to get the value of "short" in addition to updating, then you should probably do it as two queries instead - a SELECT to get "short", and an UPDATE to update the rows after.

Answer 3

If i try to run your query on sqlfiddle.com i get the error: "You can't specify target table 'idtabelle' for update in FROM clause".
But you can wrap your subquery into another subquery (derived table):
UPDATE idtabelle
SET position = position-1
WHERE short IN (SELECT short FROM (
SELECT short
FROM idtabelle
WHERE idnumber = :idV
) temp);
http://sqlfiddle.com/#!9/7d88a/1