diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index 9c140a6..ab1e4ce 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -42,7 +42,7 @@
 
 	public $dbdriver = 'pdo';
 
-	// the character used to excape - not necessary for PDO
+	// The character used to escaping
 	protected $_escape_char = '"';
 
 	// clause and character used for LIKE escape sequences
@@ -62,6 +62,14 @@
 	// need to track the PDO options
 	public $options = array();
 
+	/**
+	 * Constructor
+	 *
+	 * Validates the DSN string and/or detects the subdriver
+	 *
+	 * @param	array
+	 * @return	void
+	 */
 	public function __construct($params)
 	{
 		parent::__construct($params);
@@ -71,14 +79,17 @@
 			// If there is a minimum valid dsn string pattern found, we're done
 			// This is for general PDO users, who tend to have a full DSN string.
 			$this->subdriver = $match[1];
+			return;
 		}
-		else
+		// Legacy support for DSN specified in the hostname field
+		elseif (preg_match('/([^;]+):/', $this->hostname, $match) && count($match) === 2)
 		{
-			// Try to build a complete DSN string from params
-			$this->_connect_string($params);
+			$this->dsn = $this->hostname;
+			$this->hostname = NULL;
+			$this->subdriver = $match[1];
+			return;
 		}
-
-		if (in_array($this->subdriver, array('mssql', 'sybase'), TRUE))
+		elseif (in_array($this->subdriver, array('mssql', 'sybase'), TRUE))
 		{
 			$this->subdriver = 'dblib';
 		}
@@ -86,52 +97,19 @@
 		{
 			$this->subdriver = '4d';
 		}
-
-		// clause and character used for LIKE escape sequences
-		// this one depends on the driver being used
-		if ($this->subdriver === 'odbc')
+		elseif ( ! in_array($this->subdriver, array('4d', 'cubrid', 'dblib', 'firebird', 'ibm', 'informix', 'mysql', 'oci', 'odbc', 'sqlite', 'sqlsrv'), TRUE))
 		{
-			$this->_escape_char = '';
-			$this->_like_escape_str = " {escape '%s'} ";
-		}
-	}
+			log_message('error', 'PDO: Invalid or non-existent subdriver');
 
-	/**
-	 * Connection String
-	 *
-	 * @param	array
-	 * @return	void
-	 */
-	protected function _connect_string($params)
-	{
-		if (strpos($this->hostname, ':'))
-		{
-			// hostname generally would have this prototype
-			// $db['hostname'] = 'subdriver:host(/Server(/DSN))=hostname(/DSN);';
-			// We need to get the prefix (subdriver used by PDO).
-			$dsnarray = explode(':', $this->hostname);
-			$this->subdriver = $dsnarray[0];
-
-			// End dsn with a semicolon for extra backward compability
-			// if database property was not empty.
-			if ( ! empty($this->database))
+			if ($this->db_debug)
 			{
-				$this->dsn .= rtrim($this->hostname, ';').';';
-			}
-		}
-		else
-		{
-			// Invalid DSN, display an error
-			if ( ! array_key_exists('subdriver', $params))
-			{
-				show_error('Invalid DB Connection String for PDO');
+				show_error('Invalid or non-existent PDO subdriver');
 			}
 
-			// Assuming that the following DSN string format is used:
-			// $dsn = 'pdo://username:password@hostname:port/database?subdriver=pgsql';
-			$this->dsn = $this->subdriver.':';
-
+			throw new Exception('Invalid or non-existent PDO subdriver');
 		}
+
+		$this->dsn = NULL;
 	}
 
 	// --------------------------------------------------------------------
@@ -330,43 +308,6 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Show table query
-	 *
-	 * Generates a platform-specific query string so that the table names can be fetched
-	 *
-	 * @param	bool
-	 * @return	string
-	 */
-	protected function _list_tables($prefix_limit = FALSE)
-	{
-		$sql = 'SHOW TABLES FROM '.$this->escape_identifiers($this->database);
-
-		if ($prefix_limit !== FALSE AND $this->dbprefix !== '')
-		{
-			return FALSE;
-		}
-
-		return $sql;
-	}
-
-	// --------------------------------------------------------------------
-
-	/**
-	 * Show column query
-	 *
-	 * Generates a platform-specific query string so that the column names can be fetched
-	 *
-	 * @param	string	the table name
-	 * @return	string
-	 */
-	protected function _list_columns($table = '')
-	{
-		return 'SHOW COLUMNS FROM '.$this->escape_identifiers($table);
-	}
-
-	// --------------------------------------------------------------------
-
-	/**
 	 * Field data query
 	 *
 	 * Generates a platform-specific query so that the column data can be retrieved
@@ -376,7 +317,7 @@
 	 */
 	protected function _field_data($table)
 	{
-		return 'SELECT TOP 1 FROM '.$this->escape_identifiers($table);
+		return 'SELECT TOP 1 * FROM '.$this->protect_identifiers($table);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php b/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
index 3a2679f..a3e1181 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
@@ -85,6 +85,32 @@
 	// --------------------------------------------------------------------
 
 	/**
+	 * Non-persistent database connection
+	 *
+	 * @param	bool
+	 * @return	object
+	 */
+	public function db_connect($persistent = FALSE)
+	{
+		$pdo_obj = parent::db_connect($persistent);
+
+		if ( ! is_object($pdo_obj))
+		{
+			return $pdo_obj;
+		}
+
+		// Determine how identifiers are escaped
+		$query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');
+		$query = $query->row_array();
+		$this->_quoted_identifier = empty($query) ? FALSE : (bool) $query['qi'];
+		$this->_escape_char = ($this->_quoted_identifier) ? '"' : array('[', ']');
+
+		return $pdo_obj;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Show table query
 	 *
 	 * Generates a platform-specific query string so that the table names can be fetched
@@ -119,22 +145,9 @@
 	 */
 	protected function _list_columns($table = '')
 	{
-		return 'SELECT "column_name" FROM "information_schema"."columns" WHERE "table_name" = '.$this->escape($table);
-	}
-
-	// --------------------------------------------------------------------
-
-	/**
-	 * Field data query
-	 *
-	 * Generates a platform-specific query so that the column data can be retrieved
-	 *
-	 * @param	string	the table name
-	 * @return	string
-	 */
-	protected function _field_data($table)
-	{
-		return 'SELECT TOP 1 * FROM '.$this->protect_identifiers($table);
+		return 'SELECT '.$this->escape_identifiers('column_name')
+				.' FROM '.$this->escape_identifiers('information_schema.columns')
+				.' WHERE '.$this->escape_identifiers('table_name').' = '.$this->escape($table);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php b/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php
new file mode 100644
index 0000000..a4f9dad
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php
@@ -0,0 +1,239 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 3.0.0
+ * @filesource
+ */
+
+/**
+ * PDO ODBC Database Adapter Class
+ *
+ * Note: _DB is an extender class that the app controller
+ * creates dynamically based on whether the query builder
+ * class is being used or not.
+ *
+ * @package		CodeIgniter
+ * @subpackage	Drivers
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_odbc_driver extends CI_DB_pdo_driver {
+
+	public $subdriver = 'odbc';
+
+	// The character used for escaping - not used in ODBC
+	protected $_escape_char = '';
+
+	// clause and character used for LIKE escape sequences
+	protected $_like_escape_chr = '!';
+	protected $_like_escape_str = " {escape '%s'} ";
+
+	protected $_random_keyword = ' RAND()';
+
+	/**
+	 * Constructor
+	 *
+	 * Builds the DSN if not already set.
+	 *
+	 * @param	array
+	 * @return	void
+	 */
+	public function __construct($params)
+	{
+		parent::__construct($params);
+
+		if (empty($this->dsn))
+		{
+			$this->dsn = $params['subdriver'].':host='.(empty($this->hostname) ? '127.0.0.1' : $this->hostname);
+
+			if ( ! empty($this->port))
+			{
+				$this->dsn .= (DIRECTORY_SEPARATOR === '\\' ? ',' : ':').$this->port;
+			}
+
+			empty($this->database) OR $this->dsn .= ';dbname='.$this->database;
+			empty($this->char_set) OR $this->dsn .= ';charset='.$this->char_set;
+			empty($this->appname) OR $this->dsn .= ';appname='.$this->appname;
+		}
+		else
+		{
+			if ( ! empty($this->char_set) && strpos($this->dsn, 'charset=', 6) === FALSE)
+			{
+				$this->dsn .= ';charset='.$this->char_set;
+			}
+
+			$this->subdriver = 'odbc';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Show table query
+	 *
+	 * Generates a platform-specific query string so that the table names can be fetched
+	 *
+	 * @param	bool
+	 * @return	string
+	 */
+	protected function _list_tables($prefix_limit = FALSE)
+	{
+		$sql = "SELECT table_name FROM information_schema.tables WHERE table_schema = 'public'";
+
+		if ($prefix_limit !== FALSE && $this->dbprefix !== '')
+		{
+			return $sql." AND table_name LIKE '".$this->escape_like_str($this->dbprefix)."%' "
+				.sprintf($this->_like_escape_str, $this->_like_escape_chr);
+		}
+
+                return $sql;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Show column query
+	 *
+	 * Generates a platform-specific query string so that the column names can be fetched
+	 *
+	 * @param	string	the table name
+	 * @return	string
+	 */
+	protected function _list_columns($table = '')
+	{
+		return 'SELECT column_name FROM information_schema.columns WHERE table_name = '.$this->escape($table);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * From Tables
+	 *
+	 * This function implicitly groups FROM tables so there is no confusion
+	 * about operator precedence in harmony with SQL standards
+	 *
+	 * @param	array
+	 * @return	string
+	 */
+	protected function _from_tables($tables)
+	{
+		return is_array($tables) ? implode(', ', $tables) : $tables;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Update statement
+	 *
+	 * Generates a platform-specific update string from the supplied data
+	 *
+	 * @param	string	the table name
+	 * @param	array	the update data
+	 * @param	array	the where clause
+	 * @param	array	the orderby clause (ignored)
+	 * @param	array	the limit clause (ignored)
+	 * @param	array	the like clause
+	 * @return	string
+         */
+	protected function _update($table, $values, $where, $orderby = array(), $limit = FALSE, $like = array())
+	{
+		foreach ($values as $key => $val)
+		{
+			$valstr[] = $key.' = '.$val;
+		}
+
+		$where = empty($where) ? '' : ' WHERE '.implode(' ', $where);
+
+		if ( ! empty($like))
+		{
+			$where .= ($where === '' ? ' WHERE ' : ' AND ').implode(' ', $like);
+		}
+
+		return 'UPDATE '.$table.' SET '.implode(', ', $valstr).$where;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Truncate statement
+	 *
+	 * Generates a platform-specific truncate string from the supplied data
+	 *
+	 * If the database does not support the truncate() command,
+	 * then this method maps to 'DELETE FROM table'
+	 *
+	 * @param	string	the table name
+	 * @return	string
+	 */
+	protected function _truncate($table)
+	{
+		return 'DELETE FROM '.$table;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Delete statement
+	 *
+	 * Generates a platform-specific delete string from the supplied data
+	 *
+	 * @param	string	the table name
+	 * @param	array	the where clause
+	 * @param	array	the like clause
+	 * @param	string	the limit clause
+	 * @return	string
+	 */
+	protected function _delete($table, $where = array(), $like = array(), $limit = FALSE)
+	{
+		$conditions = array();
+
+		empty($where) OR $conditions[] = implode(' ', $where);
+		empty($like) OR $conditions[] = implode(' ', $like);
+
+		$conditions = (count($conditions) > 0) ? ' WHERE '.implode(' AND ', $conditions) : '';
+
+		return 'DELETE FROM '.$table.$conditions;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Limit string
+	 *
+	 * Generates a platform-specific LIMIT clause
+	 *
+	 * @param	string	the sql query string
+	 * @param	int	the number of rows to limit the query to
+	 * @param	int	the offset value
+	 * @return	string
+	 */
+	protected function _limit($sql, $limit, $offset)
+	{
+		return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);
+	}
+
+}
+
+/* End of file pdo_odbc_driver.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php b/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
index 59ae853..7486e42 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
@@ -97,7 +97,7 @@
 	 */
 	protected function _list_tables($prefix_limit = FALSE)
 	{
-		$sql = 'SELECT * FROM "information_schema"."tables" WHERE "table_schema" = \'public\'';
+		$sql = 'SELECT "table_name" FROM "information_schema"."tables" WHERE "table_schema" = \'public\'';
 
 		if ($prefix_limit === TRUE && $this->dbprefix !== '')
 		{
diff --git a/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
index 5afd749..a1865b5 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
@@ -174,22 +174,9 @@
 	 */
 	protected function _list_columns($table = '')
 	{
-		return 'SELECT "column_name" FROM "information_schema"."columns" WHERE "table_name" = '.$this->escape($table);
-	}
-
-	// --------------------------------------------------------------------
-
-	/**
-	 * Field data query
-	 *
-	 * Generates a platform-specific query so that the column data can be retrieved
-	 *
-	 * @param	string	the table name
-	 * @return	string
-	 */
-	protected function _field_data($table)
-	{
-		return 'SELECT TOP 1 * FROM '.$this->protect_identifiers($table);
+		return 'SELECT '.$this->escape_identifiers('column_name')
+			.' FROM '.$this->escape_identifiers('information_schema.columns')
+			.' WHERE '.$this->escape_identifiers('table_name').' = '.$this->escape($table);
 	}
 
 	// --------------------------------------------------------------------