system/database/drivers/sqlsrv/sqlsrv_driver.php - code-igniter-v3-giggi - Gitiles

 <?php
 /**
  * CodeIgniter
  *
  * An open source application development framework for PHP
  *
  * This content is released under the MIT License (MIT)
  *
  * Copyright (c) 2014 - 2018, British Columbia Institute of Technology
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  *
  * @package	CodeIgniter
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2018, British Columbia Institute of Technology (http://bcit.ca/)
  * @license	http://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 2.0.3
  * @filesource
  */
 defined('BASEPATH') OR exit('No direct script access allowed');

 /**
  * SQLSRV 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		https://codeigniter.com/user_guide/database/
  */
 class CI_DB_sqlsrv_driver extends CI_DB {

 	/**
 	 * Database driver
 	 *
 	 * @var	string
 	 */
 	public $dbdriver = 'sqlsrv';

 	/**
 	 * Scrollable flag
 	 *
 	 * Determines what cursor type to use when executing queries.
 	 *
 	 * FALSE or SQLSRV_CURSOR_FORWARD would increase performance,
 	 * but would disable num_rows() (and possibly insert_id())
 	 *
 	 * @var	mixed
 	 */
 	public $scrollable;

 	// --------------------------------------------------------------------

 	/**
 	 * ORDER BY random keyword
 	 *
 	 * @var	array
 	 */
 	protected $_random_keyword = array('NEWID()', 'RAND(%d)');

 	/**
 	 * Quoted identifier flag
 	 *
 	 * Whether to use SQL-92 standard quoted identifier
 	 * (double quotes) or brackets for identifier escaping.
 	 *
 	 * @var	bool
 	 */
 	protected $_quoted_identifier = TRUE;

 	// --------------------------------------------------------------------

 	/**
 	 * Class constructor
 	 *
 	 * @param	array	$params
 	 * @return	void
 	 */
 	public function __construct($params)
 	{
 		parent::__construct($params);

 		// This is only supported as of SQLSRV 3.0
 		if ($this->scrollable === NULL)
 		{
 			$this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED')
 				? SQLSRV_CURSOR_CLIENT_BUFFERED
 				: FALSE;
 		}
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Database connection
 	 *
 	 * @param	bool	$pooling
 	 * @return	resource
 	 */
 	public function db_connect($pooling = FALSE)
 	{
 		$charset = in_array(strtolower($this->char_set), array('utf-8', 'utf8'), TRUE)
 			? 'UTF-8' : SQLSRV_ENC_CHAR;

 		$connection = array(
 			'UID'			=> empty($this->username) ? '' : $this->username,
 			'PWD'			=> empty($this->password) ? '' : $this->password,
 			'Database'		=> $this->database,
 			'ConnectionPooling'	=> ($pooling === TRUE) ? 1 : 0,
 			'CharacterSet'		=> $charset,
 			'Encrypt'		=> ($this->encrypt === TRUE) ? 1 : 0,
 			'ReturnDatesAsStrings'	=> 1
 		);

 		// If the username and password are both empty, assume this is a
 		// 'Windows Authentication Mode' connection.
 		if (empty($connection['UID']) && empty($connection['PWD']))
 		{
 			unset($connection['UID'], $connection['PWD']);
 		}

 		if (FALSE !== ($this->conn_id = sqlsrv_connect($this->hostname, $connection)))
 		{
 			// 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 $this->conn_id;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Select the database
 	 *
 	 * @param	string	$database
 	 * @return	bool
 	 */
 	public function db_select($database = '')
 	{
 		if ($database === '')
 		{
 			$database = $this->database;
 		}

 		if ($this->_execute('USE '.$this->escape_identifiers($database)))
 		{
 			$this->database = $database;
 			$this->data_cache = array();
 			return TRUE;
 		}

 		return FALSE;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Execute the query
 	 *
 	 * @param	string	$sql	an SQL query
 	 * @return	resource
 	 */
 	protected function _execute($sql)
 	{
 		return ($this->scrollable === FALSE OR $this->is_write_type($sql))
 			? sqlsrv_query($this->conn_id, $sql)
 			: sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => $this->scrollable));
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Begin Transaction
 	 *
 	 * @return	bool
 	 */
 	protected function _trans_begin()
 	{
 		return sqlsrv_begin_transaction($this->conn_id);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Commit Transaction
 	 *
 	 * @return	bool
 	 */
 	protected function _trans_commit()
 	{
 		return sqlsrv_commit($this->conn_id);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Rollback Transaction
 	 *
 	 * @return	bool
 	 */
 	protected function _trans_rollback()
 	{
 		return sqlsrv_rollback($this->conn_id);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Affected Rows
 	 *
 	 * @return	int
 	 */
 	public function affected_rows()
 	{
 		return sqlsrv_rows_affected($this->result_id);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Insert ID
 	 *
 	 * Returns the last id created in the Identity column.
 	 *
 	 * @return	string
 	 */
 	public function insert_id()
 	{
 		return $this->query('SELECT SCOPE_IDENTITY() AS insert_id')->row()->insert_id;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Database version number
 	 *
 	 * @return	string
 	 */
 	public function version()
 	{
 		if (isset($this->data_cache['version']))
 		{
 			return $this->data_cache['version'];
 		}

 		if ( ! $this->conn_id OR ($info = sqlsrv_server_info($this->conn_id)) === FALSE)
 		{
 			return FALSE;
 		}

 		return $this->data_cache['version'] = $info['SQLServerVersion'];
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * List table query
 	 *
 	 * Generates a platform-specific query string so that the table names can be fetched
 	 *
 	 * @param	bool
 	 * @return	string	$prefix_limit
 	 */
 	protected function _list_tables($prefix_limit = FALSE)
 	{
 		$sql = 'SELECT '.$this->escape_identifiers('name')
 			.' FROM '.$this->escape_identifiers('sysobjects')
 			.' WHERE '.$this->escape_identifiers('type')." = 'U'";

 		if ($prefix_limit === TRUE && $this->dbprefix !== '')
 		{
 			$sql .= ' AND '.$this->escape_identifiers('name')." LIKE '".$this->escape_like_str($this->dbprefix)."%' "
 				.sprintf($this->_escape_like_str, $this->_escape_like_chr);
 		}

 		return $sql.' ORDER BY '.$this->escape_identifiers('name');
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * List column query
 	 *
 	 * Generates a platform-specific query string so that the column names can be fetched
 	 *
 	 * @param	string	$table
 	 * @return	string
 	 */
 	protected function _list_columns($table = '')
 	{
 		return 'SELECT COLUMN_NAME
 			FROM INFORMATION_SCHEMA.Columns
 			WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Returns an object with field data
 	 *
 	 * @param	string	$table
 	 * @return	array
 	 */
 	public function field_data($table)
 	{
 		$sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
 			FROM INFORMATION_SCHEMA.Columns
 			WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

 		if (($query = $this->query($sql)) === FALSE)
 		{
 			return FALSE;
 		}
 		$query = $query->result_object();

 		$retval = array();
 		for ($i = 0, $c = count($query); $i < $c; $i++)
 		{
 			$retval[$i]			= new stdClass();
 			$retval[$i]->name		= $query[$i]->COLUMN_NAME;
 			$retval[$i]->type		= $query[$i]->DATA_TYPE;
 			$retval[$i]->max_length		= ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
 			$retval[$i]->default		= $query[$i]->COLUMN_DEFAULT;
 		}

 		return $retval;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Error
 	 *
 	 * Returns an array containing code and message of the last
 	 * database error that has occurred.
 	 *
 	 * @return	array
 	 */
 	public function error()
 	{
 		$error = array('code' => '00000', 'message' => '');
 		$sqlsrv_errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);

 		if ( ! is_array($sqlsrv_errors))
 		{
 			return $error;
 		}

 		$sqlsrv_error = array_shift($sqlsrv_errors);
 		if (isset($sqlsrv_error['SQLSTATE']))
 		{
 			$error['code'] = isset($sqlsrv_error['code']) ? $sqlsrv_error['SQLSTATE'].'/'.$sqlsrv_error['code'] : $sqlsrv_error['SQLSTATE'];
 		}
 		elseif (isset($sqlsrv_error['code']))
 		{
 			$error['code'] = $sqlsrv_error['code'];
 		}

 		if (isset($sqlsrv_error['message']))
 		{
 			$error['message'] = $sqlsrv_error['message'];
 		}

 		return $error;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Update statement
 	 *
 	 * Generates a platform-specific update string from the supplied data
 	 *
 	 * @param	string	$table
 	 * @param	array	$values
 	 * @return	string
 	 */
 	protected function _update($table, $values)
 	{
 		$this->qb_limit = FALSE;
 		$this->qb_orderby = array();
 		return parent::_update($table, $values);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Truncate statement
 	 *
 	 * Generates a platform-specific truncate string from the supplied data
 	 *
 	 * If the database does not support the TRUNCATE statement,
 	 * then this method maps to 'DELETE FROM table'
 	 *
 	 * @param	string	$table
 	 * @return	string
 	 */
 	protected function _truncate($table)
 	{
 		return 'TRUNCATE TABLE '.$table;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Delete statement
 	 *
 	 * Generates a platform-specific delete string from the supplied data
 	 *
 	 * @param	string	$table
 	 * @return	string
 	 */
 	protected function _delete($table)
 	{
 		if ($this->qb_limit)
 		{
 			return 'WITH ci_delete AS (SELECT TOP '.$this->qb_limit.' * FROM '.$table.$this->_compile_wh('qb_where').') DELETE FROM ci_delete';
 		}

 		return parent::_delete($table);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * LIMIT
 	 *
 	 * Generates a platform-specific LIMIT clause
 	 *
 	 * @param	string	$sql	SQL Query
 	 * @return	string
 	 */
 	protected function _limit($sql)
 	{
 		// As of SQL Server 2012 (11.0.*) OFFSET is supported
 		if (version_compare($this->version(), '11', '>='))
 		{
 			// SQL Server OFFSET-FETCH can be used only with the ORDER BY clause
 			empty($this->qb_orderby) && $sql .= ' ORDER BY 1';

 			return $sql.' OFFSET '.(int) $this->qb_offset.' ROWS FETCH NEXT '.$this->qb_limit.' ROWS ONLY';
 		}

 		$limit = $this->qb_offset + $this->qb_limit;

 		// An ORDER BY clause is required for ROW_NUMBER() to work
 		if ($this->qb_offset && ! empty($this->qb_orderby))
 		{
 			$orderby = $this->_compile_order_by();

 			// We have to strip the ORDER BY clause
 			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

 			// Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
 			if (count($this->qb_select) === 0 OR strpos(implode(',', $this->qb_select), '*') !== FALSE)
 			{
 				$select = '*'; // Inevitable
 			}
 			else
 			{
 				// Use only field names and their aliases, everything else is out of our scope.
 				$select = array();
 				$field_regexp = ($this->_quoted_identifier)
 					? '("[^\"]+")' : '(\[[^\]]+\])';
 				for ($i = 0, $c = count($this->qb_select); $i < $c; $i++)
 				{
 					$select[] = preg_match('/(?:\s|\.)'.$field_regexp.'$/i', $this->qb_select[$i], $m)
 						? $m[1] : $this->qb_select[$i];
 				}
 				$select = implode(', ', $select);
 			}

 			return 'SELECT '.$select." FROM (\n\n"
 				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.trim($orderby).') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
 				."\n\n) ".$this->escape_identifiers('CI_subquery')
 				."\nWHERE ".$this->escape_identifiers('CI_rownum').' BETWEEN '.($this->qb_offset + 1).' AND '.$limit;
 		}

 		return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Insert batch statement
 	 *
 	 * Generates a platform-specific insert string from the supplied data.
 	 *
 	 * @param	string	$table	Table name
 	 * @param	array	$keys	INSERT keys
 	 * @param	array	$values	INSERT values
 	 * @return	string|bool
 	 */
 	protected function _insert_batch($table, $keys, $values)
 	{
 		// Multiple-value inserts are only supported as of SQL Server 2008
 		if (version_compare($this->version(), '10', '>='))
 		{
 			return parent::_insert_batch($table, $keys, $values);
 		}

 		return ($this->db_debug) ? $this->display_error('db_unsupported_feature') : FALSE;
 	}

 	// --------------------------------------------------------------------

 	/**
 	 * Close DB Connection
 	 *
 	 * @return	void
 	 */
 	protected function _close()
 	{
 		sqlsrv_close($this->conn_id);
 	}

 }
	<?php
	/**
	* CodeIgniter
	*
	* An open source application development framework for PHP
	*
	* This content is released under the MIT License (MIT)
	*
	* Copyright (c) 2014 - 2018, British Columbia Institute of Technology
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*
	* @package CodeIgniter
	* @author EllisLab Dev Team
	* @copyright Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
	* @copyright Copyright (c) 2014 - 2018, British Columbia Institute of Technology (http://bcit.ca/)
	* @license http://opensource.org/licenses/MIT MIT License
	* @link https://codeigniter.com
	* @since Version 2.0.3
	* @filesource
	*/
	defined('BASEPATH') OR exit('No direct script access allowed');

	/**
	* SQLSRV 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 https://codeigniter.com/user_guide/database/
	*/
	class CI_DB_sqlsrv_driver extends CI_DB {

	/**
	* Database driver
	*
	* @var string
	*/
	public $dbdriver = 'sqlsrv';

	/**
	* Scrollable flag
	*
	* Determines what cursor type to use when executing queries.
	*
	* FALSE or SQLSRV_CURSOR_FORWARD would increase performance,
	* but would disable num_rows() (and possibly insert_id())
	*
	* @var mixed
	*/
	public $scrollable;

	// --------------------------------------------------------------------

	/**
	* ORDER BY random keyword
	*
	* @var array
	*/
	protected $_random_keyword = array('NEWID()', 'RAND(%d)');

	/**
	* Quoted identifier flag
	*
	* Whether to use SQL-92 standard quoted identifier
	* (double quotes) or brackets for identifier escaping.
	*
	* @var bool
	*/
	protected $_quoted_identifier = TRUE;

	// --------------------------------------------------------------------

	/**
	* Class constructor
	*
	* @param array $params
	* @return void
	*/
	public function __construct($params)
	{
	parent::__construct($params);

	// This is only supported as of SQLSRV 3.0
	if ($this->scrollable === NULL)
	{
	$this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED')
	? SQLSRV_CURSOR_CLIENT_BUFFERED
	: FALSE;
	}
	}

	// --------------------------------------------------------------------

	/**
	* Database connection
	*
	* @param bool $pooling
	* @return resource
	*/
	public function db_connect($pooling = FALSE)
	{
	$charset = in_array(strtolower($this->char_set), array('utf-8', 'utf8'), TRUE)
	? 'UTF-8' : SQLSRV_ENC_CHAR;

	$connection = array(
	'UID' => empty($this->username) ? '' : $this->username,
	'PWD' => empty($this->password) ? '' : $this->password,
	'Database' => $this->database,
	'ConnectionPooling' => ($pooling === TRUE) ? 1 : 0,
	'CharacterSet' => $charset,
	'Encrypt' => ($this->encrypt === TRUE) ? 1 : 0,
	'ReturnDatesAsStrings' => 1
	);

	// If the username and password are both empty, assume this is a
	// 'Windows Authentication Mode' connection.
	if (empty($connection['UID']) && empty($connection['PWD']))
	{
	unset($connection['UID'], $connection['PWD']);
	}

	if (FALSE !== ($this->conn_id = sqlsrv_connect($this->hostname, $connection)))
	{
	// 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 $this->conn_id;
	}

	// --------------------------------------------------------------------

	/**
	* Select the database
	*
	* @param string $database
	* @return bool
	*/
	public function db_select($database = '')
	{
	if ($database === '')
	{
	$database = $this->database;
	}

	if ($this->_execute('USE '.$this->escape_identifiers($database)))
	{
	$this->database = $database;
	$this->data_cache = array();
	return TRUE;
	}

	return FALSE;
	}

	// --------------------------------------------------------------------

	/**
	* Execute the query
	*
	* @param string $sql an SQL query
	* @return resource
	*/
	protected function _execute($sql)
	{
	return ($this->scrollable === FALSE OR $this->is_write_type($sql))
	? sqlsrv_query($this->conn_id, $sql)
	: sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => $this->scrollable));
	}

	// --------------------------------------------------------------------

	/**
	* Begin Transaction
	*
	* @return bool
	*/
	protected function _trans_begin()
	{
	return sqlsrv_begin_transaction($this->conn_id);
	}

	// --------------------------------------------------------------------

	/**
	* Commit Transaction
	*
	* @return bool
	*/
	protected function _trans_commit()
	{
	return sqlsrv_commit($this->conn_id);
	}

	// --------------------------------------------------------------------

	/**
	* Rollback Transaction
	*
	* @return bool
	*/
	protected function _trans_rollback()
	{
	return sqlsrv_rollback($this->conn_id);
	}

	// --------------------------------------------------------------------

	/**
	* Affected Rows
	*
	* @return int
	*/
	public function affected_rows()
	{
	return sqlsrv_rows_affected($this->result_id);
	}

	// --------------------------------------------------------------------

	/**
	* Insert ID
	*
	* Returns the last id created in the Identity column.
	*
	* @return string
	*/
	public function insert_id()
	{
	return $this->query('SELECT SCOPE_IDENTITY() AS insert_id')->row()->insert_id;
	}

	// --------------------------------------------------------------------

	/**
	* Database version number
	*
	* @return string
	*/
	public function version()
	{
	if (isset($this->data_cache['version']))
	{
	return $this->data_cache['version'];
	}

	if ( ! $this->conn_id OR ($info = sqlsrv_server_info($this->conn_id)) === FALSE)
	{
	return FALSE;
	}

	return $this->data_cache['version'] = $info['SQLServerVersion'];
	}

	// --------------------------------------------------------------------

	/**
	* List table query
	*
	* Generates a platform-specific query string so that the table names can be fetched
	*
	* @param bool
	* @return string $prefix_limit
	*/
	protected function _list_tables($prefix_limit = FALSE)
	{
	$sql = 'SELECT '.$this->escape_identifiers('name')
	.' FROM '.$this->escape_identifiers('sysobjects')
	.' WHERE '.$this->escape_identifiers('type')." = 'U'";

	if ($prefix_limit === TRUE && $this->dbprefix !== '')
	{
	$sql .= ' AND '.$this->escape_identifiers('name')." LIKE '".$this->escape_like_str($this->dbprefix)."%' "
	.sprintf($this->_escape_like_str, $this->_escape_like_chr);
	}

	return $sql.' ORDER BY '.$this->escape_identifiers('name');
	}

	// --------------------------------------------------------------------

	/**
	* List column query
	*
	* Generates a platform-specific query string so that the column names can be fetched
	*
	* @param string $table
	* @return string
	*/
	protected function _list_columns($table = '')
	{
	return 'SELECT COLUMN_NAME
	FROM INFORMATION_SCHEMA.Columns
	WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));
	}

	// --------------------------------------------------------------------

	/**
	* Returns an object with field data
	*
	* @param string $table
	* @return array
	*/
	public function field_data($table)
	{
	$sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
	FROM INFORMATION_SCHEMA.Columns
	WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

	if (($query = $this->query($sql)) === FALSE)
	{
	return FALSE;
	}
	$query = $query->result_object();

	$retval = array();
	for ($i = 0, $c = count($query); $i < $c; $i++)
	{
	$retval[$i] = new stdClass();
	$retval[$i]->name = $query[$i]->COLUMN_NAME;
	$retval[$i]->type = $query[$i]->DATA_TYPE;
	$retval[$i]->max_length = ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
	$retval[$i]->default = $query[$i]->COLUMN_DEFAULT;
	}

	return $retval;
	}

	// --------------------------------------------------------------------

	/**
	* Error
	*
	* Returns an array containing code and message of the last
	* database error that has occurred.
	*
	* @return array
	*/
	public function error()
	{
	$error = array('code' => '00000', 'message' => '');
	$sqlsrv_errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);

	if ( ! is_array($sqlsrv_errors))
	{
	return $error;
	}

	$sqlsrv_error = array_shift($sqlsrv_errors);
	if (isset($sqlsrv_error['SQLSTATE']))
	{
	$error['code'] = isset($sqlsrv_error['code']) ? $sqlsrv_error['SQLSTATE'].'/'.$sqlsrv_error['code'] : $sqlsrv_error['SQLSTATE'];
	}
	elseif (isset($sqlsrv_error['code']))
	{
	$error['code'] = $sqlsrv_error['code'];
	}

	if (isset($sqlsrv_error['message']))
	{
	$error['message'] = $sqlsrv_error['message'];
	}

	return $error;
	}

	// --------------------------------------------------------------------

	/**
	* Update statement
	*
	* Generates a platform-specific update string from the supplied data
	*
	* @param string $table
	* @param array $values
	* @return string
	*/
	protected function _update($table, $values)
	{
	$this->qb_limit = FALSE;
	$this->qb_orderby = array();
	return parent::_update($table, $values);
	}

	// --------------------------------------------------------------------

	/**
	* Truncate statement
	*
	* Generates a platform-specific truncate string from the supplied data
	*
	* If the database does not support the TRUNCATE statement,
	* then this method maps to 'DELETE FROM table'
	*
	* @param string $table
	* @return string
	*/
	protected function _truncate($table)
	{
	return 'TRUNCATE TABLE '.$table;
	}

	// --------------------------------------------------------------------

	/**
	* Delete statement
	*
	* Generates a platform-specific delete string from the supplied data
	*
	* @param string $table
	* @return string
	*/
	protected function _delete($table)
	{
	if ($this->qb_limit)
	{
	return 'WITH ci_delete AS (SELECT TOP '.$this->qb_limit.' * FROM '.$table.$this->_compile_wh('qb_where').') DELETE FROM ci_delete';
	}

	return parent::_delete($table);
	}

	// --------------------------------------------------------------------

	/**
	* LIMIT
	*
	* Generates a platform-specific LIMIT clause
	*
	* @param string $sql SQL Query
	* @return string
	*/
	protected function _limit($sql)
	{
	// As of SQL Server 2012 (11.0.*) OFFSET is supported
	if (version_compare($this->version(), '11', '>='))
	{
	// SQL Server OFFSET-FETCH can be used only with the ORDER BY clause
	empty($this->qb_orderby) && $sql .= ' ORDER BY 1';

	return $sql.' OFFSET '.(int) $this->qb_offset.' ROWS FETCH NEXT '.$this->qb_limit.' ROWS ONLY';
	}

	$limit = $this->qb_offset + $this->qb_limit;

	// An ORDER BY clause is required for ROW_NUMBER() to work
	if ($this->qb_offset && ! empty($this->qb_orderby))
	{
	$orderby = $this->_compile_order_by();

	// We have to strip the ORDER BY clause
	$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

	// Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
	if (count($this->qb_select) === 0 OR strpos(implode(',', $this->qb_select), '*') !== FALSE)
	{
	$select = '*'; // Inevitable
	}
	else
	{
	// Use only field names and their aliases, everything else is out of our scope.
	$select = array();
	$field_regexp = ($this->_quoted_identifier)
	? '("[^\"]+")' : '(\[[^\]]+\])';
	for ($i = 0, $c = count($this->qb_select); $i < $c; $i++)
	{
	$select[] = preg_match('/(?:\s\|\.)'.$field_regexp.'$/i', $this->qb_select[$i], $m)
	? $m[1] : $this->qb_select[$i];
	}
	$select = implode(', ', $select);
	}

	return 'SELECT '.$select." FROM (\n\n"
	.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.trim($orderby).') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
	."\n\n) ".$this->escape_identifiers('CI_subquery')
	."\nWHERE ".$this->escape_identifiers('CI_rownum').' BETWEEN '.($this->qb_offset + 1).' AND '.$limit;
	}

	return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);
	}

	// --------------------------------------------------------------------

	/**
	* Insert batch statement
	*
	* Generates a platform-specific insert string from the supplied data.
	*
	* @param string $table Table name
	* @param array $keys INSERT keys
	* @param array $values INSERT values
	* @return string\|bool
	*/
	protected function _insert_batch($table, $keys, $values)
	{
	// Multiple-value inserts are only supported as of SQL Server 2008
	if (version_compare($this->version(), '10', '>='))
	{
	return parent::_insert_batch($table, $keys, $values);
	}

	return ($this->db_debug) ? $this->display_error('db_unsupported_feature') : FALSE;
	}

	// --------------------------------------------------------------------

	/**
	* Close DB Connection
	*
	* @return void
	*/
	protected function _close()
	{
	sqlsrv_close($this->conn_id);
	}

	}