php+mysql 日期的写入读出操作

$conn_string = array ('server'=>'127.0.0.1','user'=>'root','password'=>'1230');
$conn = mysql_connect($conn_string['server'],$conn_string['user'],$conn_string['password']);
mysql_select_db('test');
try
{
    $now = date("Y-m-d 14:20:00");
    $select_sql = "select name,insert_time from test where insert_time>'".$now."'";
    $select_stmt = mysql_query($select_sql);
    while($row = mysql_fetch_assoc($select_stmt))
    {
        print_r($row);
    }

    $count_sql = "select count(id) from test where insert_time>'".$now."'";
    $count_stmt = mysql_query($count_sql);
    $count_num = mysql_fetch_row($count_stmt);
    print_r($count_num);
}

        $now = date("Y-m-d H:i:s");
        $sql = "INSERT INTO test (`name` ,`insert_time` ) VALUES ('".$i."', '".$now."')";
        $stmt = mysql_query ($sql);

关于mysql中日期datetime的操作测试。