time management

[Curiousguy]

how do i set a variable for time and minus two different time??

For example : a class on 9:00am to 10:00am, and the class is only available to log on from 8:30am to 9:30am. how do i using the SQL statement do this?

PLs help.... thanks vry much

<? 


$hour = date("H");
$min = date("i");
$Connect = mysql_connect('localhost','root','');
    mysql_select_db('mw');
    $result=mysql_query("SELECT * FROM student WHERE '$hour:$min' > before  AND '$hour:$min' < after");
        echo"<form name=main method=POST action=verify_attendance.php>";
	if ($result != Null)
	{
		echo "<TABLE width=\"100%\" CELLSPACING=\"0\" CELLPADDING=\"0\" BORDER=\"1\" align=center>";
		echo "<TR><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">Username</font></TD><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">Start</font></TD><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">End</font></TD><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">Date</font></TD><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">Subject</font></TD><TD width=\"12%\" align=center height=\"30\"><font face=\"Arial Narrow\"><font size=\"4\">Programme</font></TD></TR>\n";	
	}
    while ($number_of_array = mysql_fetch_array($result)) 
    {

			echo "<tr>\n"; 
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[username1]</font></TD>\n";
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[startime]</font></TD>\n";
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[endtime]</font></TD>\n"; 
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[date]</font></TD>\n";
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[subject]</font></TD>\n"; 
			echo "<TD align=center><font face=\"Arial Narrow\"><font size=\"3\">$number_of_array[programme]</font></TD>\n"; 
			echo "<td align=center><font face=\"Arial Narrow\"><form name=\"main\" method=\"post\" action=\"verify_attendance.php\username1=$number_of_array[username1]&startime=$number_of_array[startime]&endtime=$number_of_array[endtime]&date=$number_of_array[date]&subject=$number_of_array[subject]&programme=$number_of_array[programme]\" onClick=\"return confirm('Are you sure you want to delete this record?  ');\"><br><input type=\"submit\" name=\"Submit\" value=\"Mark\" ></form></font></TD>\n";				
}

?>

[stolzyboy]

have you looked into BETWEEN, below is a snippet from mysql.com

expr BETWEEN min AND max
If expr is greater than or equal to min and expr is less than or
equal to max, BETWEEN returns 1, otherwise it returns 0. This is
equivalent to the expression (min <= expr AND expr <= max) if all
the arguments are of the same type. Otherwise type conversion
takes place, according to the rules above, but applied to all the
three arguments. Note that before 4.0.5 arguments were
converted to the type of expr instead.

mysql> SELECT 1 BETWEEN 2 AND 3;
-> 0
mysql> SELECT 'b' BETWEEN 'a' AND 'c';
-> 1
mysql> SELECT 2 BETWEEN 2 AND '3';
-> 1
mysql> SELECT 2 BETWEEN 2 AND 'x-3';
-> 0
expr NOT BETWEEN min AND max
Same as NOT (expr BETWEEN min AND max).