What's causing this Warning?

[LGD]

Can anyone tell me what's wrong with this piece of code?
PHP is returning this warning: "Supplied argument is not a valid MySQL result resource ..." in the line with **

If I quote the first query, the code runs perfectly... I can't figure out what might be interfering with the second query...

---

$query_cat = mysql_query("SELECT nome FROM categorias WHERE id_categoria = $cat",$db);
$cat = mysql_fetch_assoc($query_cat);

echo "<b>".$cat["nome"]."</b><br><br>";


$query = mysql_query("SELECT * FROM subcategorias WHERE id_categoria = $cat",$db);

**  if (mysql_num_rows($query)<1) { echo "<font size=\"1\">De momento não existem sub-categorias.</font><br><br>"; } **

elseif (mysql_num_rows($query)>=1) {

while ($subcat = mysql_fetch_array($query)) {
     [...]
}

[Radon3k]

Try:

$sql = "SELECT nome FROM cateogrias WHERE id_categoria = '$cat'";

$result = mysql_query($sql);

If not that, then after you have id_categoria put single quotes around the variable, as I have above.

Hope this helps,
Radon3k.

[LGD]

Nope. That's not the issue.
The problem is at this line:

 if (mysql_num_rows($query)<1) { echo "<font size=\"1\">De momento não existem sub-categorias.</font><br><br>"; }

PHP says : "Supplied argument is not a valid MySQL result resource"

But it seems to go away if I quote the first db query...

[Radon3k]

So if it goes away, does that mean it works?

[LGD]

Yeah, it works perfectly if I quote the first query, but I need it to retrieve the category name...

[Radon3k]

Why not do a SELECT * from tbl_name first, then select the specific information?

[LGD]

I've figured out what's causing the problem:
On the second line I was re-defining the variable $cat which is being used in the SQL queries...

Duh. :p

[Radon3k]

Glad you figured it out. 🙂