[RESOLVED] mysql_num_rows() small problem

[david.mitchell]

Hi guys i have this pretty straight peice of code, that checks if it brought back any rows so i can change what dropdown options become available.

$queryvoid = $this->db->query("SELECT * FROM 'test' WHERE test_id = '1' GROUP BY width ORDER BY width");
$num_rows = mysql_num_rows($queryvoid);

if ($num_rows > 0 ){ echo "Results exist<br>"; } 

but this returns an error

mysql_num_rows(): supplied argument is not a valid MySQL result resource 

is there something im missing with this?

Regards
David

[NogDog]

It means that the MySQL server choked on your query for one reason or another, so mysql_query() returned Boolean false instead of a query result resource.

In other words, check the result for false, and if so, do whatever sort of debugging you prefer at that point.

[LutinFou]

Hi,
I'm no expert but for the code you have supplied, it looks like you are not running your query. Before you count your rows you will need to run the query :
$r=mysql_query($queryvoid);

mysql_num_rows function takes only one argument: the query result variable (i.e. $r in this case), therefore you code should read:

$num_rows=mysql_num_rows($r);

try that and see if it works
regards
LF

[NogDog]

Hi,
I'm no expert but for the code you have supplied, it looks like you are not running your query. Before you count your rows you will need to run the query :
$r=mysql_query($queryvoid);

mysql_num_rows function takes only one argument: the query result variable (i.e. $r in this case), therefore you code should read:

$num_rows=mysql_num_rows($r);

try that and see if it works
regards
LF

Good point, in that on a second look, I see the original code executes the query via an unknown (to me at this point) object method $this->db->query. It may be that this is not even a mysql_query() call, in which case mysql_num_rows() is of no use at this point. Instead you would need to use whatever the comparable method is for that db object you are using.

[david.mitchell]

it ended up being

$queryvoid = $this->db->query("SELECT * FROM 'test' WHERE test_id = '1'"); 
$num_rows = $this->test->num_rows; 

if ($num_rows > 0 ){ echo "Results exist<br>"; } 

Thanks guys