Fatal error: Class 'MergeQuery' not found in D:\education\php\drupal\includes\database\database.inc on line 718

I am presently trying to install Drupal for the first time with the intention of working through the tutorials in Sams Teach Yourself Drupal in 24 Hours.

Since I am new to Drupal and this book seems like it will include some coverage of version 7, I thought I would start with the "latest", rather than learn on an older version and need to retrain.

I dumped Drupal into a directory at:

D:\education\php\drupal

I configured a virtual server on Apache 2.2 to work with this directory:

  <virtualhost 127.0.0.1:59090>
    ServerName drupal.localhost
#    ServerRoot "D:\education\php\drupal"
    DocumentRoot "D:\education\php\drupal"
    DirectoryIndex index.php

    <directory "D:\education\php\drupal">
       AllowOverRide All
       Allow from All
    </directory>
  </virtualhost>

I created a database and configured the settings.php to find it:

with

$databases = array (
      'driver' => 'mysql',
      'database' => 'drupal',
      'username' => 'root2',
      'password' => 'fll192ws',
      'host' => 'localhost',
      'port' => '53336',
);

$db_prefix = 'drupal_';

I ran the install.php.

I had a bunch of errors on the page to configure the database the first few times I saw it, but after tweaking the settings.php file and the database and going back to the start of install.php a few times, something seemed to click and I was able to "complete" the process, at least in the sense that if I try to run install.php, eventually I reach a page headed "Drupal already installed".

The install process evidently modified settings.php such that:

$databases = array (
  'default' => 
  array (
    'default' => 
    array (
      'driver' => 'mysql',
      'database' => 'drupal',
      'username' => 'root2',
      'password' => 'fll192ws',
      'host' => 'localhost',
      'port' => '53336',
    ),
  ),
);

and it also added tables to the drupal schemata.

However, if I go to index.php, instead of anything useful, I see an error which states:

Fatal error: Class 'MergeQuery' not found in D:\education\php\drupal\includes\database\database.inc on line 718

and I have no idea how to get past this.