Finding Max number in database

[Tissy]

I have what I thought was a simple php script which would show the maximum number stored in a database.

The database is a temperature logger which just contains time and date and the read temperature.

When I call this php script I get a Resource #5 error. As I'm still learning php, can anyone assist where I have gone wrong please as it looks simple?

Thank you

<?php
require_once("config.inc.php");
if (!$completed) die("Please edit config.inc.php before using this.");

//Connect to database
$con = mysql_connect($dbHost, $dbUser, $dbPass);
if (!$con)
{
	die('Could not connect: ' . mysql_error());
}

//Check if database exists
if (!mysql_select_db($dbDatabase, $con))
{
	die("Could not select database");
}

$query = "SELECT MAX(temp) FROM `temp`";
$result = mysql_query($query);
$num = mysql_numrows($result);

echo $result;
?>

[Derokorian]

$result is a result resource, which means when you echo it you get the string "Resource #" followed by a number representing the resource in memory. You need to fetch a row from the result set and then get the value from that.

Additionally, DO NOT USE THE mysql_* extension, it has been deprecated for sometime as well as highly discouraged for even longer. See my signature for a tutorial I wrote on using mysqli (the i stands for improved), though I do highly recommend getting into PDO as soon as you can.

[Tissy]

Thank you Derokorian for the reply, I'm obviously getting it round my next. Very new to SQL etc.

This return -0, so getting there I guess as no error.

<?php
require_once("config.inc.php");
if (!$completed) die("Please edit config.inc.php before using this.");

//Connect to database
$con = mysql_connect($dbHost, $dbUser, $dbPass);
if (!$con)
{
	die('Could not connect: ' . mysql_error());
}

//Check if database exists
if (!mysql_select_db($dbDatabase, $con))
{
	die("Could not select database");
}

$query = "SELECT MAX(temp) FROM $dbMainTable";
$result = mysql_query($query);
$num = mysql_numrows($result);

$output .= "<temperature>" . round(mysql_result($result, int, $rowTemperature),1) . "</temperature>";

echo $output;
?>

Where am I still going wrong please?

[jkurrle]

$query = "SELECT MAX(temp) as maxtemp FROM $dbMainTable";
$result = mysql_query($query);
$row = mysql_fetch_assoc($result);
echo $maxtemp;

[NogDog]

$output .= "<temperature>" . round(mysql_result($result, 0),1) . "</temperature>";

Fro mysql_result, row numbers start at 0, and the 3rd parameter will default to the first column if omitted. ([man]mysql_result[/man])

[laserlight]

I second Derokorian's recommendation: switch to PDO or MySQLi right now. No point learning something that is long outdated and does not provide value over what is newer.

[dalecosp]

<?php
require_once("config.inc.php");
if (!$completed) die("Please edit config.inc.php before using this.");

//Connect to database
$con = mysqli_connect( $dbHost, $dbUser, $dbPass, $dbDatabase );
if (!$con)   die('Could not connect: ' . mysqli_error($con));


$query = "SELECT MAX(temp) as tempmax FROM $dbMainTable";
$result = mysqli_query( $con, $query );

if ($result) {
   $row = $result->fetch_assoc();
   $high_temp = $row['tempmax'];
} else {
   echo "<p>No result.  SQL is: $query.</p><p>Error from DB server: ".$mysqli_error($con)."</p>";
   echo "<p>Data dump:  Host $dbhost - User $dbUser - Pass omitted, Database $dbDatabase, Table $dbMainTable</p>";
   exit;
}

echo "<temperature>$high_temp</temperature>";