Как сделать выбор возраста от и до в таблице БД в ячейке которая указывает возраст?

if($age >=18 && $age < 30

$age =($_POST["age"]);
echo $age;
if ($age >= 18 && $age < 30) {
//
} elseif($age >= 30 && $age < 45) {
//
} else {
//
}

$result = mysql_query("SELECT * FROM users WHERE `age` > 10 AND `age` < 100");

$age =($_POST["age"]);
echo $age;
if ($age >= 18 && $age < 30) {
//
} elseif($age >= 30 && $age < 45) {
//
} else {
//
}

$result = mysql_query("SELECT * FROM users WHERE `age` > 10 AND `age` < 100");

<?php 
$con = mysql_connect("localhost","......... ","........ ");
if (!$con)
   {
   die('Could not connect: ' . mysql_error());
   }
mysql_select_db("........", $con);
$sql = mysql_query("SET CHARACTER SET cp1251_koi8");
$result = mysql_query("SELECT * FROM users WHERE `age` > 10 AND `age` < 100");
mysql_query($order);
echo $myrow_comcont['title'];
echo $myrow_comcont['com'];
echo "<table border='1'>";
 
$key_array = array('Fam','Name','Otch','age','cvet');
$sort_array = array('asc','desc');
 
if (isset($_GET['key']))
{
    $key=$_GET['key'];
    $sort=$_GET['sort'];
}
else
{
    $key='Fam';
    $sort='desc';
}
 
if(in_array($key, $key_array) && in_array($sort, $sort_array))
{
    $query = "SELECT * FROM users ORDER BY $key $sort";     
    $result = mysql_query($query);
}
else exit("неверный формат запроса!"); 
 
if($sort=='asc')
{
   $sort='desc';
   $vid_sort=$sort_up;
}
else
{
   $sort='asc';
   $vid_sort=$sort_down;   
}
 
print "<table border = 1>";
print "<tr>
<th width='50'><a href=\"word5.php?key=Fam&sort=$sort\">Fam</a></th>
<th width='50'><a href=\"word5.php?key=Name&sort=$sort\">Name</a></th>
<th width='50'><a href=\"word5.php?key=Otch&sort=$sort\">Otch</a></th>
<th width='160'><a href=\"word5.php?key=age&sort=$sort \">age</a>От<label><input name= age type= text  size = 1 /></label>
До<label><input name= age type= text  size = 1 /></label></th>
<th width='50'><a href=\"word5.php?key=cvet&sort=$sort\">cvet</a></th>
</th></tr>";
// Отформатировать и вывести каждую строку таблицы
while ($row = mysql_fetch_array($result))
{
    print "<tr>";
    print '<td>'.$row['Fam'].'</td><td>'.$row['Name'].'</td><td>'.$row['Otch'].'</td><td>'.$row['age'].'</td><td>'.substr($row['cvet'],0,30).'</td></td>';
    $age =($_POST["age"]);
echo $age;
if ($age >= 18 && $age < 30) {
     // 
} elseif($age >= 30 && $age < 45) {
     //
} else {
    // 
}
    print "</tr>";
}
// Завершить таблицу
print "</table>";

$_GET['key'] == 'age'

$_GET['age_first'] и $_GET['age_second']

$between = ' WHERE age BETWEEN '.$age_first.' AND '.$age_second.' '

$_GET['key'] == 'age'   
if (isset($_GET['key']))
{
    $key=$_GET['key'];
    $age_first = $_GET['age_first'];
    $age_second = $_GET['age_second'];
}
else
{