counting fields

[FiveFlat]

I want to query a table that keeps track of when a horse gets ridden and for how many hours it was ridden.
So, for instance if the horse named joe got ridden yesterday for 1.5 hours and again today for .5 hours, I want to see that it was ridden for a total of 2 hours.
How do I do that?

[stolzyboy]

$query = "select sum(fieldname) as horse_hours;";
$result = mysql_query($query) or die(mysql_error());

$row = mysql_fetch_array($result);

echo $row['horse_hours'];

[Sxooter]

Simple, something like:

select sum(hours_ridden) from horsies where horse='Mr Ed.' and day_ridden='2003-08-05';

Or over periods of time:

and day_ridden>='2003-08-05' and day_ridden<=2003-08-08';

[FiveFlat]

Okay,
I written this code here, but when a horse is selected and submit is clicked the whole page refreshes and runs the query with the first horse in the list.
AND to add to it all, I get this error when I include the "AND rider='$shname' " in the query "$rides"

Warning: mysql_numrows(): supplied argument is not a valid MySQL result resource in /var/www/html/ridetime1.php on line 97

<form method="post" action="<?php $PHP_SELF ?>">
<?php
$hourqry=mysql_query("SELECT * FROM horse");
echo '<td>Horse:<select name=hhours>';
while ($hrow = @mysql_fetch_assoc($hourqry))
{
echo "<option value=\"$hrow[reg_num]\">$hrow[reg_name]</option>\n";
}
echo '</select></td></tr><tr><td>';
echo ("<input type=Submit name=rsubmit value=Show></form>");
if ($rsubmit) {
$shname=$_SESSION['username'];
$rides=mysql_query("SELECT * FROM ridehours WHERE reg_num='$hhours' AND rider='$shname'");
$hournum=mysql_numrows($rides);
$hr=0;
while ($hr < $hournum) {
$date=mysql_result($rides,$hr,"date");
$rider=mysql_result($rides,$hr,"rider");
$ridelocation=mysql_result($rides,$hr,"ridelocation");
$hours=mysql_result($rides,$hr,"hours");
echo ("$date<br>$rider | $ridelocation | $hours<br>");
++$hr;
 }
} else {
echo ("Please select a horse to view hours you've ridden.");
}
?>