In this tutorial, you will the steps that ar needed to not only learn but create a simple but effective database management system.

Simple DB Management System

Here is a simple dbms that I made.

<?php
class db
{
    function connect()
    {
        include($_SERVER['DOCUMENT_ROOT'] . '/config.inc.php');
        switch($type)
        {
            case "mysql":
                mysql_connect($host, $user, $pass) or die("Could not connect: " . mysql_error());
                mysql_select_db($name) or die(mysql_error());
                break;
            case "mssql":                mssql_connect($host, $user, $pass) or die("Could not connect!");
                mssql_select_db($name);
                break;
            case "oracle":
                $_SESSION['con'] = oci_connect($host, $user, $pass, $name);
                break;
        }
    }
    function query($q)
    {
        include($_SERVER['DOCUMENT_ROOT'] . '/config.inc.php');
        switch($type)
        {
            case "mysql":
                return mysql_query($q);
                break;
            case "mssql":
                return mssql_query($q);
                break;
            case "oracle":
                return oci_parse($_SESSION['con'], $q);
                break;
        }
    }
    function numrows($q)
    {
        include($_SERVER['DOCUMENT_ROOT'] . '/config.inc.php');
        switch($type)
        {
            case "mysql":
                return mysql_num_rows($q);
                break;
            case "mssql":
                return mssql_num_rows($q);
                break;
            case "oracle":
                return oci_num_rows($q);
                break;
        }
    }
    function fetcharray($q)
    {
        include($_SERVER['DOCUMENT_ROOT'] . '/config.inc.php');
        switch($type)
        {
            case "mysql":
                return mysql_fetch_array($q);
                break;
            case "mssql":
                return mssql_fetch_array($q);
                break;
            case "oracle":
                return oci_fetch_array($q);
                break;
        }
    }
    /* Use this before inserting into database */
    function sanitize($dirty)
    {
        $dirty = trim($dirty);
        $dirty = htmlspecialchars($dirty);
        include($_SERVER['DOCUMENT_ROOT'] . '/config.inc.php');
        switch($type)
        {
            case "mysql":
                $dirty = mysql_real_escape_string($dirty);
                break;
            case "mssql":
                $dirty = mysql_real_escape_string($dirty);
                break;
            case "oracle":
                $dirty = mysql_real_escape_string($dirty);
                break;
        }
        return $dirty;
    }
    /* Use this before displaying database data */
    function scrub($dirty)
    {
        $dirty = stripslashes($dirty);
        return $dirty;
    }
}
?>

Save that as dbms.php.

Create a file called config.inc.php and put it in the site root.

Put the following code inside:

<?php
/* Config File  */
$host="your_host";
$name="your_db"; 
$user="your_user";
$pass="your_pass";
$pfix="your_db_prefix";
$type="db_type";
?>

Replace your_host with your database host.
Replace your_db with your database name.
Replace your_user with your database username.
Replace your_pass with your database password.
Replace your_db_prefix with the table prefix.
Replace db_type with either mysql, mssql, or oracle.

In the the files you want to access the database. Include the dbms file. Then add the following code:

$db &= new db;
$db->connect();
$db->query("SELECT * FROM...");   

Replace SELECT * FROM... with the query you want to perform. Check the dbms php file for more functions.

Use your new dbms wisely.