PHP mysql update limit?

[impin]

Table: cquestions
cqid, cqtext, showdate.

I want to update 'showdate' field to tomorrows date..

database:

    cqid    cqtext    showdate
    200    q1    2013-05-22
    201    q2    0000-00-00
    202    q3    0000-00-00

the code will display q1. i want to update the 2nd row only to

201    q2    2013-05-23

so, tomorrow q2 will be displayed and the third
row will be updated as

202    q3    2013-05-24

<?php
$today=date("Y/m/d");
$tomorrow= date("Y-m-d", strtotime("tomorrow"));
echo "<form method='post' id='submit' action='checkresult.php'>";
$sql="SELECT * FROM cquestions where showdate= '$today' limit 1";
$result=mysql_query($sql);
while ($row = mysql_fetch_array($result)) {
    $cqid=mysql_result($result,"cqid");
$update1="update cquestions set showdate='$tomorrow' where showdate='0000-00-00' and cqid!='$cqid' order by cqid limit 1";
mysql_query($update1);
 
echo "<p>" . $row['cqtext'] . "</p>";
$sql2="SELECT * FROM canswers where cqid=".$row['cqid'];
$result2=mysql_query($sql2);
while($row2=mysql_fetch_assoc($result2)){
echo "<input type='radio' name='".$row['cqid']."' value='".$row2['cqans']."' />".$row2['aatext']; }
/*echo "<input type='hidden' name='email' value='email' />";*/
}
echo"<input type='submit' id='submit' name='submit' value='Submit Answers' />";
echo "</form>";
?>

this code update the next row, but the problem is its executed every time page loads and update the next row... i want to execute the update query only once for the day. how to do it?

[Rabbit]

Store the last time it was updated and if that was today, don't run the update.

[Luuk]

or, only run the update if
"SELECT * FROM cquestions where showdate= '$today'"
did not return a result
(which means there is no record for today...)

[impin]

i have stored the last_update and checked with the current date. i want to run the update query only once.

updated code:

$last_update = date("Y/m/d");
if($last_update==$today)
{
$update1="update cquestions set showdate='$tomorrow' where showdate='0000-00-00' and cqid!='$cqid' order by cqid limit 1";
mysql_query($update1);
$update2="update qupdate set last_update='$tomorrow'";
mysql_query($update2);
$sql3="SELECT * FROM qupdate";
$result=mysql_query($sql3);
$last_update=mysql_result($result,"last_update");    
echo "$last_update";
}

last_update was stored in the table ($update2="update qupdate set last_update='$tomorrow'";). first its executing correctly but next time last_update was set to today's date. (($last_update = date("Y/m/d");)) its not set to the last updated date. so the if condition executing all the time. how to fix it?
i want to run the update query only once...

[impin]

fixed it. but if i change the limit to 2, it doesn't working. only one row is displaying. first two rows should be displayed...

$sql="SELECT * FROM cquestions where showdate= '$today' limit 1";

$today=date("Y-m-d");
$sql4="SELECT * FROM qupdate";
$result=mysql_query($sql4);
$last_update=mysql_result($result,"last_update");    
$tomorrow= date("Y-m-d", strtotime("tomorrow"));
echo "$last_update";
echo "<form method='post' id='submit' action='checkresult.php'>";
$sql="SELECT * FROM cquestions where showdate= '$today' limit 1";
$result=mysql_query($sql);
while ($row = mysql_fetch_array($result)) {
$cqid=mysql_result($result,"cqid");    
if($last_update==$today)
{
$update1="update cquestions set showdate='$tomorrow' where showdate='0000-00-00' and cqid!='$cqid' order by cqid limit 1";
mysql_query($update1);
$update2="update qupdate set last_update='$tomorrow'";
mysql_query($update2);
$sql3="SELECT * FROM qupdate";
$result=mysql_query($sql3);
$last_update=mysql_result($result,"last_update");    
echo "$last_update";
}

[Luuk]

It fout want to store the last update date in 'qupdate',
Than you should 1st check what the currenlty stored date is ("select ... from qupdate "), and compare that date with today

If the dates are not equal, than you should update 'qupdate' with the date for today.

After above exercise, you should be able to get the (3) questions for today....