PHP, MySQL, PDO - Get result from UPDATE query?

Question

I am updating a row in a table, and trying to return the updated row, as per this SO answer.

My code is the following:

$sql = \"SET @update_id := \'\         


        

Answer 1

You need to do the SELECT @update_id as a separate query -- you can't put multiple queries in a single statement. So do:

$sql = "SET @update_id := '';
        UPDATE testing SET status='1', id=(SELECT @update_id:=id)
        WHERE status='0' LIMIT 1";
try{
    $db->beginTransaction();
    $db->query($sql); // no need for prepare/execute since there are no parameters
    $stmt = $db->query("SELECT @update_id");
    $row = $stmt->fetch(PDO::FETCH_ASSOC);
    $id = $row['@update_id'];
    $db->commit();
} catch (Exception $e) {
    echo $e->getMessage();
    $db->rollBack();
    exit();
}

Answer 2

You're right about getting the exception SQLSTATE[HY000] for $stmt->rowCount();

The problem is, you cannot fetch an UPDATE query because these queries simply don't return values. To circumvent this, use rowCount().

As written in the PHP documentation, PDOStatement::rowCount() returns the number of rows affected by a DELETE, INSERT, or UPDATE statement.

Check out this example.

<?php
/* Updating rows from the PICNIC table*/
$update = $dbh->prepare('UPDATE ... PICNIC');
$update->execute();

/* Return the number of rows affected */
   echo $updateCount = $update->rowCount();

?>

Answer 3

It's failing on ->fetchAll() because an UPDATE query does not return any rows/data.

What you want to do, is check out PDO::rowCount(). This returns the count of how many rows have been affected by your query.

echo $stmt->rowCount();

^{This was posted assuming you're trying to check if your query was successful.}