mysql_num_rows() error

[marcnyc]

I am getting an error with the script I am trying to modify.
The error says:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/virtual/site372/fst/var/www/html/reviews/lib/class_reviews.inc on line 199

The lines of that file are as follows:

199 $resource = mysql_query($sql, $this->mysql_stream);
200 if ( mysql_num_rows($resource) == 0 )
201 return "The query did not produce any results.";

Any suggestions?
I am not sure what $this->mysql_stream does, I don't quite understand that part myself, because it's not code I have writte, I am just modifying it, but I can tell you that the variable $sql contains the query to the database in for of "SELECT ... WHERE" etc etc

[laserlight]

It could be that your SQL query is incorrect.
You can check with mysql_error()

$this->mysql_stream should refer to an open connection link that is stored as a member variable of your object.

If there isnt a connection, then you also have a problem.

[marcnyc]

Thank you very much, that was a very good suggestion. I used that function so I knew what the problem was and was able to correct it.