PHP warning - mysql_num_rows()

vexx

I'm on Mysql 5.0.51a-community and i get the following php warning

PHP Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/test/public_html/admin/testphp.php on line 24

The php code:

if(mysql_num_rows(mysql_query("SELECT file FROM datadb WHERE file='".$fileurl."' LIMIT 0,1"))==0)

NogDog

The error means your query failed to be processed by MySQL due to some sort of syntax error (i.e., MySQL returned an error instead of a query result).

It will be easier to debug if you separate the pieces out into separate commands instead of compressing them into a one-liner.

$sql = "SELECT file FROM datadb WHERE file='".$fileurl."' LIMIT 0,1";
$result = mysql_query($sql);
if($result == false)
{
   user_error(mysql_error()."<br />\n$sql");
   // output some sort of error here, possibly also die()/exit()
}
if(mysql_num_rows($result) == 0)
{

vexx

just followed your advice:

if(mysql_num_rows($results)==0)

is the problem

bradgrafelman

Okay, so what is the error message and query? That was the whole crux of NogDog's advice - get MySQL to output some error messages so you can debug the query.