Why num_rows giving two different result?

[rajeshkr]

Hi,

I am little bit confuse with the result of num_rows that i used in my code.

My table invoice have no value in current because i want to check if no value in the table.

Here is my code

 

code 1 gives $rowc value as 0 that is correct.

$fetch1="select * from invoice"; 
$val1=$con->query($fetch1); 
$rowc=$val1->num_rows; 
echo $rowc;  

Code 2 gives $rowc value as 1 that is incorrect.

$fetch1="select max(id) as id, order_no from invoice"; 
$val1=$con->query($fetch1); 
$rowc=$val1->num_rows; 
echo $rowc;  

I just want to know why the result giving two different values.
Thanks

 

[Barand]

If you use an aggregation function, such as MAX, you will get 1 row returned containing the max value, even if that value is 0