CODEWITHSUNDEEP
phpmysqlsyntax
2xAA
2xAA

Reputation: 308

MySQL syntax error, but only when using through PHP

I'm trying to re-hash user IDs in my database, but I'm getting stuck.

<?php
include("session.php");
include("functions.php");
$conn = ConnectMySQL();
setTimezone($session->username);

$sql = "SELECT username, userid FROM users";
$result = mysql_query($sql) or die(mysql_error());
while($rows = mysql_fetch_array($result)){
    $username = $rows['username'];
    $old = mysql_real_escape_string($rows['userid']);
    $new = mysql_real_escape_string($session->generateRandID());

    $moresql = "START TRANSACTION;
                UPDATE users SET userid='$new' WHERE userid='$old';
                UPDATE comments SET user='$new' WHERE user='$old';
                UPDATE forum_posts SET poster_name='$new' WHERE poster_name='$old';
                UPDATE forum_topics SET topic_poster_name='$new' WHERE topic_poster_name='$old';
                UPDATE images SET author='$new' WHERE author='$old';
                UPDATE likes SET user='$new' WHERE user='$old';
                UPDATE music SET author='$new' WHERE author='$old';
                UPDATE ratings SET user='$new' WHERE user='$old';
                COMMIT;";
    $newresult = mysql_query($moresql) or die(mysql_error());
    if(!$newresult){echo "There was a problem with changing $username's hash. \n";}
    else{echo "Changed $username's hash<i>!</i> \n";}
}
mysql_close($conn);
?>

The whole query works through PHPMyAdmin absolutely fine, just returns zero rows obviously. But when I try it with actual values being passed through it using it with PHP it gets suck:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UPDATE users SET userid='b8aca4b680707453fa4dfe1bf1d0fddb' WHERE userid='8' at line 2

There are no other errors - I'm at a loss to think of what it is. Thanks in advance,

Sam

Upvotes: 5

Views: 161

Answers (3)

Shail
Shail

Reputation: 1575

The idea I generally use when working with transactions looks like this (semi-pseudo-code) :

try {
    // First of all, let's begin a transaction
    $db->beginTransaction();

    // A set of queries ; of one fails, an exception should be thrown
    $db->query('first query');
    $db->query('second query');
    $db->query('third query');

    // If we arrive here, it means that no exception was thrown
    // i.e. no query has failed ; and we can commit the transaction
    $db->commit();
} catch (Exception $e) {
    // An exception has been thrown
    // We must rollback the transaction
    $db->rollback();
}

Note that, with this idea, if a query fails, an Exception must be thrown :

PDO can do that, depending on how you configure it See PDO::setAttribute and PDO::ATTR_ERRMODE and PDO::ERRMODE_EXCEPTION else, with some other API, you might have to test the result of the function used to execute a query, and throw an exception yourself.

Unfortunately, there is no magic involved : you cannot just put an instruction somewhere and have transactions done automatically : you still have to specific which group of queries must be executed in a transaction.

For example, quite often, you'll have a couple of queries before the transaction (before the begin), and another couple of queries after the transaction (after either commit or rollback) ; and you'll want those queries executed no matter what happened (or not) in the transaction.

=====================================================

You can use mysqli also to achieve same

For ex

<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* disable autocommit */
mysqli_autocommit($link, FALSE);

mysqli_query($link, "CREATE TABLE myCity LIKE City");
mysqli_query($link, "ALTER TABLE myCity Type=InnoDB");
mysqli_query($link, "INSERT INTO myCity SELECT * FROM City LIMIT 50");

/* commit insert */
mysqli_commit($link);

Upvotes: 1

FrankieTheKneeMan
FrankieTheKneeMan

Reputation: 6800

From the documentation:

mysql_query() sends a unique query (multiple queries are not supported)

You cant't send a series of queries to the database through php. Consider writing a procedure on your actual database and then calling that from php.

Also, those functions are deprecated. You should consider a different library. PDO is a popular one.

Upvotes: 2

rationalboss
rationalboss

Reputation: 5389

Multiple queries are not supported by mysql_query(). You must execute one query at a time. See http://php.net/manual/en/function.mysql-query.php

Upvotes: 7

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