Subversion-Projekte lars-tiefland.prado

<?php

/**

 * TMsssqlCommandBuilder class file.

 *

 * @author Wei Zhuo <weizhuo[at]gmail[dot]com>

 * @link http://www.pradosoft.com/

 * @copyright Copyright © 2005-2008 PradoSoft

 * @license http://www.pradosoft.com/license/

 * @version $Id: TDbCommandBuilder.php 1863 2007-04-12 12:43:49Z wei $

 * @package System.Data.Common

 */

Prado::using('System.Data.Common.TDbCommandBuilder');

/**

 * TMssqlCommandBuilder provides specifics methods to create limit/offset query commands

 * for MSSQL servers.

 *

 * @author Wei Zhuo <weizho[at]gmail[dot]com>

 * @version $Id: TDbCommandBuilder.php 1863 2007-04-12 12:43:49Z wei $

 * @package System.Data.Common

 * @since 3.1

 */

class TMssqlCommandBuilder extends TDbCommandBuilder

{

	/**

	 * Overrides parent implementation. Uses "SELECT @@Identity".

	 * @return integer last insert id, null if none is found.

	 */

	public function getLastInsertID()

	{

		foreach($this->getTableInfo()->getColumns() as $column)

		{

			if($column->hasSequence())

			{

				$command = $this->getDbConnection()->createCommand('SELECT @@Identity');

				return intval($command->queryScalar());

			}

		}

	}

	/**

	 * Overrides parent implementation. Alters the sql to apply $limit and $offset.

	 * The idea for limit with offset is done by modifying the sql on the fly

	 * with numerous assumptions on the structure of the sql string.

	 * The modification is done with reference to the notes from

	 * http://troels.arvin.dk/db/rdbms/#select-limit-offset

	 *

	 * <code>

	 * SELECT * FROM (

	 *  SELECT TOP n * FROM (

	 *    SELECT TOP z columns      -- (z=n+skip)

	 *    FROM tablename

	 *    ORDER BY key ASC

	 *  ) AS FOO ORDER BY key DESC -- ('FOO' may be anything)

	 * ) AS BAR ORDER BY key ASC    -- ('BAR' may be anything)

	 * </code>

	 *

	 * <b>Regular expressions are used to alter the SQL query. The resulting SQL query

	 * may be malformed for complex queries.</b> The following restrictions apply

	 *

	 * <ul>

	 *   <li>

	 * In particular, <b>commas</b> should <b>NOT</b>

	 * be used as part of the ordering expression or identifier. Commas must only be

	 * used for separating the ordering clauses.

	 *  </li>

	 *  <li>

	 * In the ORDER BY clause, the column name should NOT be be qualified

	 * with a table name or view name. Alias the column names or use column index.

	 * </li>

	 * <li>

	 * No clauses should follow the ORDER BY clause, e.g. no COMPUTE or FOR clauses.

	 * </li>

	 *

	 * @param string SQL query string.

	 * @param integer maximum number of rows, -1 to ignore limit.

	 * @param integer row offset, -1 to ignore offset.

	 * @return string SQL with limit and offset.

	 */

	public function applyLimitOffset($sql, $limit=-1, $offset=-1)

	{

		$limit = $limit!==null ? intval($limit) : -1;

		$offset = $offset!==null ? intval($offset) : -1;

		if ($limit > 0 && $offset <= 0) //just limit

			$sql = preg_replace('/^([\s(])*SELECT( DISTINCT)?(?!\s*TOP\s*\()/i',"\\1SELECT\\2 TOP $limit", $sql);

		else if($limit > 0 && $offset > 0)

			$sql = $this->rewriteLimitOffsetSql($sql, $limit,$offset);

		return $sql;

	}

	/**

	 * Rewrite sql to apply $limit > and $offset > 0 for MSSQL database.

	 * See http://troels.arvin.dk/db/rdbms/#select-limit-offset

	 * @param string sql query

	 * @param integer $limit > 0

	 * @param integer $offset > 0

	 * @return sql modified sql query applied with limit and offset.

	 */

	protected function rewriteLimitOffsetSql($sql, $limit, $offset)

	{

		$fetch = $limit+$offset;

		$sql = preg_replace('/^([\s(])*SELECT( DISTINCT)?(?!\s*TOP\s*\()/i',"\\1SELECT\\2 TOP $fetch", $sql);

		$ordering = $this->findOrdering($sql);

		$orginalOrdering = $this->joinOrdering($ordering);

		$reverseOrdering = $this->joinOrdering($this->reverseDirection($ordering));

		$sql = "SELECT * FROM (SELECT TOP {$limit} * FROM ($sql) as [__inner top table__] {$reverseOrdering}) as [__outer top table__] {$orginalOrdering}";

		return $sql;

	}

	/**

	 * Base on simplified syntax http://msdn2.microsoft.com/en-us/library/aa259187(SQL.80).aspx

	 *

	 * @param string $sql

	 * @return array ordering expression as key and ordering direction as value

	 */

	protected function findOrdering($sql)

	{

		if(!preg_match('/ORDER BY/i', $sql))

			return array();

		$matches=array();

		$ordering=array();

		preg_match_all('/(ORDER BY)[\s"\[](.*)(ASC|DESC)?(?:[\s"\[]|$|COMPUTE|FOR)/i', $sql, $matches);

		if(count($matches)>1 && count($matches[2]) > 0)

		{

			$parts = explode(',', $matches[2][0]);

			foreach($parts as $part)

			{

				$subs=array();

				if(preg_match_all('/(.*)[\s"\]](ASC|DESC)$/i', trim($part), $subs))

				{

					if(count($subs) > 1 && count($subs[2]) > 0)

					{

						$ordering[$subs[1][0]] = $subs[2][0];

					}

					//else what?

				}

				else

					$ordering[trim($part)] = 'ASC';

			}

		}

		return $ordering;

	}

	/**

	 * @param array ordering obtained from findOrdering()

	 * @return string concat the orderings

	 */

	protected function joinOrdering($orders)

	{

		if(count($orders)>0)

		{

			$str=array();

			foreach($orders as $column => $direction)

				$str[] = $column.' '.$direction;

			return 'ORDER BY '.implode(', ', $str);

		}

	}

	/**

	 * @param array original ordering

	 * @return array ordering with reversed direction.

	 */

	protected function reverseDirection($orders)

	{

		foreach($orders as $column => $direction)

			$orders[$column] = strtolower(trim($direction))==='desc' ? 'ASC' : 'DESC';

		return $orders;

	}

}