Howto check for empty results

[thepreacher]

The results of a select statement could be empty - ie the is no data in the table matching the search string.

$result = mysql_query($query); - ie results is empty.

What will $ results contain when that happens. How do i check for empty results.

Thanks

[rdivilbiss]

False.

e.g.


       $result = mysql_query($query); - ie results is empty.
       if (!$result) {
      $message  = 'Invalid query: ' . mysql_error() . "\n";
      die($message);
   }

[CrYpTiC_MauleR]

Its been awhile, but doesn't mysql_query() only return false when the query failed as in syntax error or such, and returns true when query succeeded. So if a query succeeded in being executed it will return true even if the result was no rows, or 1 or more rows. Thats what I always have assumed from the return values for mysql_query() and that the above method is used for debugging and mysql_num_rows() is used for checking if a row was returned or not.

Code

Language: php (GeSHi-highlighted)
<?php
 
$result = mysql_query($query) or die(mysql_error());
if (0 < mysql_num_rows($result))
{
    // 1 or more rows returned
}
else
{
    // no rows returned
}
 
?>

[VGR]

yes. Rod is wrong this time ;-)

mysql_query returns false only in case of failure
in case you want to check if there were no results, mysql_num_rows() is your friend. It can ***only*** be used when the returned value of mysql_query() was TRUE, oeuf corse.

so again ther structure to use is the one explained in the online manual, ie

Code:

$linkid=mysql_connect(); // also select db etc...
$query="...";
$result=mysql_query($query,$linkid); // or die("failed on '$query' with error = ".mysql_error());
if ($result!==FALSE) { // query ok
  if (($a=mysql_num_rows($result))>0) { // dataset contains at least oen row returned
    // echo "$a rows returnd"; // now is time to use : while ($res=mysql_fetch_array($result)) { etc }
  } else { // no rows returned
    // echo "no rows returned";
  }
} else { // query failed
  // die("query failed"); ?
}

not checked against typos.