mysql_num_rows() question

Sharif

In my code block:

if (isset($id) && is_numeric($id))
	{
    		$display_news = mysql_query("SELECT html FROM news WHERE id=$id")
          or die ("MySQL Error");
     		if (mysql_num_rows($display_news) > 0)
     		{ 
        			while ($row = mysql_fetch_array($display_news)) 
        			{ 
        			    $news = $row["html"]; 
           		    echo $news; 
        			}
    			} 
    			else 
    			{ 
        			    echo("<P CLASS=\"bodytext\" ALIGN=\"CENTER\">OOX ERROR: Bad Link<BR>
		      Please <A HREF=\"javascript:history.go(-1);\" CLASS=\"bodynav\">click here</A>
		      to go back to the previous page.</P>"); 
    			}
	}
	else
	{
    		echo("<P CLASS=\"bodytext\" ALIGN=\"CENTER\">Error: No news article was selected!<BR>
		      Please <A HREF=\"javascript:history.go(-1);\" CLASS=\"bodynav\">click here</A>
		      to go back to the previous page.</P>");
	}
?>

you see an IF statement with a mysql_num_rows() specified. I am wondering why that is there.. or why I put it there in the first place... What does mysql_num_rows > 0 do to my code? Does it check the database to see if the variable needed exists or something?

khaldryck

simple enough :

mysql_num_rows gives you the number of rows returned by your query.

in this case you just test if you got at least one row .. then you display the results,
if you got no rows at all, you display the error message.

Sharif

What would this do:

mysql_num_rows($var) > 0

darkshady

$result = mysql_query("SELECT * FROM users WHERE username='darkshady'");
echo mysql_num_rows($result);

Assuming there is only one row in the table with username = darkshady then that would display one. What khaldryck said should explain it.

$var would have to be a mysql_query and then if that was in an IF statement, if there was more than 1 result then BLAH would happen.

Sharif

But what does

mysql_num_rows($var) > 0

mean then? If the amount of results returned are more than 0, then do whatever?

darkshady

Then you'll have to use an else.

if(mysql_num_rows($query)){
echo "1+ Results!";
}
else{
echo "No results!";
}