SQL/PHP Multiple querys

Question

I don't understand this because I'm just getting into query's and php.

I'm trying to get the user's ID from the database and set that equal to a different users friendreq column.

Don't worry about me not escaping properly, this is only a test so I can practice! Thank you! (Although I'm not sure what escaping is, I'm going to do my research!)

$usernameID = "SELECT Id FROM Users WHERE Username = '$username'";
$sql = "UPDATE Users SET FriendReq = $usernameID WHERE Username =  '$usernamebeingreq'";

$result = mysqli_multi_query($con, $usernameID, $sql);

if(!$result)
{ 
    echo 'Failed';
} 
else
{
    echo 'Friend added!';
}

You should not only be escaping user inserted parts of the query, but rather use prepared statements. They're the safest way of handling a query in PHP. — padarom
– padarom, Commented Jul 11, 2014 at 5:49
Thank you very much, i'll make sure to look through that, any advice on the multi query? — user3828087
– user3828087, Commented Jul 11, 2014 at 5:50
If you're just practicing why bother with this multi_query thing? Just do the queries one after the other. — quickshiftin
– quickshiftin, Commented Jul 11, 2014 at 5:55

padarom · Accepted Answer · 2014-07-11 05:55:31Z

3

According to the PHP reference of mysqli_multi_query your two queries need to be concatenated with a semicolon. You're passing each query as its own parameter.

Use the following instead:

$result = mysqli_multi_query($con, $usernameID . "; " . $sql);

This will concatenate your two queries, so that it's the following:

SELECT Id FROM Users WHERE Username = '$username'; UPDATE Users SET FriendReq = $usernameID WHERE Username =  '$usernamebeingreq'

answered Jul 11, 2014 at 5:55

padarom

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4 Comments

user3828087 Over a year ago

Worked beautifully! Thank you for all the tips, I tried to concatenate them but without the semi-colin in the middle! Thanks!!

padarom Over a year ago

@LorenzMeyer Why shouldn't it? This is what the PHP reference told us.

Lorenz Meyer Over a year ago

because $sql becomes "UPDATE Users SET FriendReq = SELECT Id FROM Users WHERE Username = '$username' WHERE Username = '$usernamebeingreq'" and $usernameID . "; " . $sql becomes

"SELECT Id FROM Users WHERE Username = '$username'; UPDATE Users SET FriendReq = SELECT Id FROM Users WHERE Username = '$username' WHERE Username =  '$usernamebeingreq'"

which is not what you want.

padarom Over a year ago

It's two queries, not one. The ; splits them and mysqli_multi_query executes them one after another.

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