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<?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;
}
}
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