pulling infomation from a database. simple error

[jeppers]

i am working on a forum script and i am trying to pull some info from a database. but i keep on getting this message

 

"Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\test\discussion\viewforum.php on line 32"

 

i have looked back through my script and can't seem to see any errors but maybe i am missing something silly. hear is my code please have a look as its completely baffled me.

 

$forumsql = "SELECT * FROM forums WHERE id = " . $validforum . ";";
$forumresult = mysql_query($forumsql);
$forumrow = mysql_fetch_assoc($forumresult);

echo "<h2>" . $forumrow['name'] . "</h2>";

echo "<a href='index.php'>" . $config_forumsname . " forums</><br /><br />";
//add a link that allows you to add a new topic to this form

echo "[<a href='newtopic.php?id= " . $validforum . "'>New Topic</a>]";
echo "<br /><br />";

$topicsql = "SELECT MAX (message.date) AS maxdate, 
topics.id AS topicid, topics.*, users.*
FROM messages, topics, users WHERE messages.topic_id
= topic.id AND topics.user_id = user.id AND 
topics.forum_id ORDER BY maxdate DESC;";
$topicresult = mysql_query($topicsql);
$topicnumrows = mysql_num_rows($topicresult); // line 32 this is where the error said it was happening....
if ($topicnumrows == 0) {
	echo "<table width='300px'><tr><td>No Topics!!</td></tr></table>";

 

hopefully you can see where i have went wrong

 

thanks

[JonnoTheDev]

check the query is correct. You should not continue to process the script if the query produces an error which is what you are doing. You need to handle errors. A simple method is:

 

if(!$result = mysql_query("SELECT ...")) {

  die(mysql_error());

}

[jeppers]

not sure how to inter great that pice of script with in my current script

 

 

if(!$result = mysql_query("SELECT ...")) {

  die(mysql_error());

}

 

any chance you could give me an example on how you would do it

 

thanks

 

 

[nitation]

@ jeppers,

 

Try this;

 

$topicsql = mysql_query("SELECT MAX (message.date) AS maxdate, 
topics.id AS topicid, topics.*, users.*
FROM messages, topics, users WHERE messages.topic_id
= topic.id AND topics.user_id = user.id AND 
topics.forum_id ORDER BY maxdate DESC") or die (mysql_error());

 

note the "or die mysql_error()); should tell where your error is coming from.

 

I also observe something in your query, why are you terminating immediately after maxdate DESC.

 

Regards

 

 

[jeppers]

well hear is what has been returned

 

FUNCTION forum.MAX does not exist.

 

not sure what to do

 

erm

 

 

[JonnoTheDev]

 

If the query is incorrect the script will terminate. If OK the results of the query are in $forumrow.

Apply to the rest of your logic.

if(!$forumresult = mysql_query($forumsql)) {
die(mysql_error());
exit();
}

$forumrow = mysql_fetch_assoc($forumresult);

[jeppers]

not sure what the problem it but the error which is poping up is still

 

 

FUNCTION forum.MAX does not exist

 

so the first query is correct but the error is within the second query. all around the MAX function

 

have you any ideas.

[jeppers]

$topicsql = "SELECT MAX(messages.date) AS maxdate, 
topics.id AS topicid, topics.*, users.*
FROM messages, topics, users WHERE messages.topic_id
= topics.id AND topics.user_id = users.id AND 
topics.forum_id ORDER BY maxdate DESC;";
if (!$topicresult = mysql_query($topicsql)) {
die(mysql_error());
exit();

 

well i found a few errors so not to bad but i have hit another error report which i have not see before.

 

 

Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause

 

i no what it means but where in the code is the issue

 

can you see it

 

[JonnoTheDev]

if you use the mysql MAX() function you have to include a GROUP BY statement. i.e.

 

SELECT MAX(fieldName) FROM table GROUP BY id ORDER BY id DESC

[jeppers]

thanks very much all done and thanks thanks for the error location tools. hope i will be able to help you soon