Subversion Repositories SmartDukaan

<?php
/**
 * MS SQL Server layer for DBO
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @package       Cake.Model.Datasource.Database
 * @since         CakePHP(tm) v 0.10.5.1790
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */

App::uses('DboSource', 'Model/Datasource');

/**
 * Dbo layer for Microsoft's official SQLServer driver
 *
 * A Dbo layer for MS SQL Server 2005 and higher. Requires the
 * `pdo_sqlsrv` extension to be enabled.
 *
 * @link http://www.php.net/manual/en/ref.pdo-sqlsrv.php
 *
 * @package       Cake.Model.Datasource.Database
 */
class Sqlserver extends DboSource {

/**
 * Driver description
 *
 * @var string
 */
        public $description = "SQL Server DBO Driver";

/**
 * Starting quote character for quoted identifiers
 *
 * @var string
 */
        public $startQuote = "[";

/**
 * Ending quote character for quoted identifiers
 *
 * @var string
 */
        public $endQuote = "]";

/**
 * Creates a map between field aliases and numeric indexes. Workaround for the
 * SQL Server driver's 30-character column name limitation.
 *
 * @var array
 */
        protected $_fieldMappings = array();

/**
 * Storing the last affected value
 *
 * @var mixed
 */
        protected $_lastAffected = false;

/**
 * Base configuration settings for MS SQL driver
 *
 * @var array
 */
        protected $_baseConfig = array(
                'persistent' => true,
                'host' => 'localhost\SQLEXPRESS',
                'login' => '',
                'password' => '',
                'database' => 'cake',
                'schema' => '',
                'flags' => array()
        );

/**
 * MS SQL column definition
 *
 * @var array
 */
        public $columns = array(
                'primary_key' => array('name' => 'IDENTITY (1, 1) NOT NULL'),
                'string' => array('name' => 'nvarchar', 'limit' => '255'),
                'text' => array('name' => 'nvarchar', 'limit' => 'MAX'),
                'integer' => array('name' => 'int', 'formatter' => 'intval'),
                'biginteger' => array('name' => 'bigint'),
                'numeric' => array('name' => 'decimal', 'formatter' => 'floatval'),
                'decimal' => array('name' => 'decimal', 'formatter' => 'floatval'),
                'float' => array('name' => 'float', 'formatter' => 'floatval'),
                'real' => array('name' => 'float', 'formatter' => 'floatval'),
                'datetime' => array('name' => 'datetime', 'format' => 'Y-m-d H:i:s', 'formatter' => 'date'),
                'timestamp' => array('name' => 'timestamp', 'format' => 'Y-m-d H:i:s', 'formatter' => 'date'),
                'time' => array('name' => 'datetime', 'format' => 'H:i:s', 'formatter' => 'date'),
                'date' => array('name' => 'datetime', 'format' => 'Y-m-d', 'formatter' => 'date'),
                'binary' => array('name' => 'varbinary'),
                'boolean' => array('name' => 'bit')
        );

/**
 * Magic column name used to provide pagination support for SQLServer 2008
 * which lacks proper limit/offset support.
 *
 * @var string
 */
        const ROW_COUNTER = '_cake_page_rownum_';

/**
 * Connects to the database using options in the given configuration array.
 *
 * @return bool True if the database could be connected, else false
 * @throws MissingConnectionException
 */
        public function connect() {
                $config = $this->config;
                $this->connected = false;

                $flags = $config['flags'] + array(
                        PDO::ATTR_PERSISTENT => $config['persistent'],
                        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
                );

                if (!empty($config['encoding'])) {
                        $flags[PDO::SQLSRV_ATTR_ENCODING] = $config['encoding'];
                }

                try {
                        $this->_connection = new PDO(
                                "sqlsrv:server={$config['host']};Database={$config['database']}",
                                $config['login'],
                                $config['password'],
                                $flags
                        );
                        $this->connected = true;
                        if (!empty($config['settings'])) {
                                foreach ($config['settings'] as $key => $value) {
                                        $this->_execute("SET $key $value");
                                }
                        }
                } catch (PDOException $e) {
                        throw new MissingConnectionException(array(
                                'class' => get_class($this),
                                'message' => $e->getMessage()
                        ));
                }

                return $this->connected;
        }

/**
 * Check that PDO SQL Server is installed/loaded
 *
 * @return bool
 */
        public function enabled() {
                return in_array('sqlsrv', PDO::getAvailableDrivers());
        }

/**
 * Returns an array of sources (tables) in the database.
 *
 * @param mixed $data The names
 * @return array Array of table names in the database
 */
        public function listSources($data = null) {
                $cache = parent::listSources();
                if ($cache !== null) {
                        return $cache;
                }
                $result = $this->_execute("SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES");

                if (!$result) {
                        $result->closeCursor();
                        return array();
                }
                $tables = array();

                while ($line = $result->fetch(PDO::FETCH_NUM)) {
                        $tables[] = $line[0];
                }

                $result->closeCursor();
                parent::listSources($tables);
                return $tables;
        }

/**
 * Returns an array of the fields in given table name.
 *
 * @param Model|string $model Model object to describe, or a string table name.
 * @return array Fields in table. Keys are name and type
 * @throws CakeException
 */
        public function describe($model) {
                $table = $this->fullTableName($model, false, false);
                $fulltable = $this->fullTableName($model, false, true);

                $cache = parent::describe($fulltable);
                if ($cache) {
                        return $cache;
                }

                $fields = array();
                $schema = is_object($model) ? $model->schemaName : false;

                $cols = $this->_execute(
                        "SELECT
                                COLUMN_NAME as Field,
                                DATA_TYPE as Type,
                                COL_LENGTH('" . ($schema ? $fulltable : $table) . "', COLUMN_NAME) as Length,
                                IS_NULLABLE As [Null],
                                COLUMN_DEFAULT as [Default],
                                COLUMNPROPERTY(OBJECT_ID('" . ($schema ? $fulltable : $table) . "'), COLUMN_NAME, 'IsIdentity') as [Key],
                                NUMERIC_SCALE as Size
                        FROM INFORMATION_SCHEMA.COLUMNS
                        WHERE TABLE_NAME = '" . $table . "'" . ($schema ? " AND TABLE_SCHEMA = '" . $schema . "'" : '')
                );

                if (!$cols) {
                        throw new CakeException(__d('cake_dev', 'Could not describe table for %s', $table));
                }

                while ($column = $cols->fetch(PDO::FETCH_OBJ)) {
                        $field = $column->Field;
                        $fields[$field] = array(
                                'type' => $this->column($column),
                                'null' => ($column->Null === 'YES' ? true : false),
                                'default' => $column->Default,
                                'length' => $this->length($column),
                                'key' => ($column->Key == '1') ? 'primary' : false
                        );

                        if ($fields[$field]['default'] === 'null') {
                                $fields[$field]['default'] = null;
                        }
                        if ($fields[$field]['default'] !== null) {
                                $fields[$field]['default'] = preg_replace(
                                        "/^[(]{1,2}'?([^')]*)?'?[)]{1,2}$/",
                                        "$1",
                                        $fields[$field]['default']
                                );
                                $this->value($fields[$field]['default'], $fields[$field]['type']);
                        }

                        if ($fields[$field]['key'] !== false && $fields[$field]['type'] === 'integer') {
                                $fields[$field]['length'] = 11;
                        } elseif ($fields[$field]['key'] === false) {
                                unset($fields[$field]['key']);
                        }
                        if (in_array($fields[$field]['type'], array('date', 'time', 'datetime', 'timestamp'))) {
                                $fields[$field]['length'] = null;
                        }
                        if ($fields[$field]['type'] === 'float' && !empty($column->Size)) {
                                $fields[$field]['length'] = $fields[$field]['length'] . ',' . $column->Size;
                        }
                }
                $this->_cacheDescription($table, $fields);
                $cols->closeCursor();
                return $fields;
        }

/**
 * Generates the fields list of an SQL query.
 *
 * @param Model $model The model to get fields for.
 * @param string $alias Alias table name
 * @param array $fields The fields so far.
 * @param bool $quote Whether or not to quote identfiers.
 * @return array
 */
        public function fields(Model $model, $alias = null, $fields = array(), $quote = true) {
                if (empty($alias)) {
                        $alias = $model->alias;
                }
                $fields = parent::fields($model, $alias, $fields, false);
                $count = count($fields);

                if ($count >= 1 && strpos($fields[0], 'COUNT(*)') === false) {
                        $result = array();
                        for ($i = 0; $i < $count; $i++) {
                                $prepend = '';

                                if (strpos($fields[$i], 'DISTINCT') !== false && strpos($fields[$i], 'COUNT') === false) {
                                        $prepend = 'DISTINCT ';
                                        $fields[$i] = trim(str_replace('DISTINCT', '', $fields[$i]));
                                }

                                if (!preg_match('/\s+AS\s+/i', $fields[$i])) {
                                        if (substr($fields[$i], -1) === '*') {
                                                if (strpos($fields[$i], '.') !== false && $fields[$i] != $alias . '.*') {
                                                        $build = explode('.', $fields[$i]);
                                                        $AssociatedModel = $model->{$build[0]};
                                                } else {
                                                        $AssociatedModel = $model;
                                                }

                                                $_fields = $this->fields($AssociatedModel, $AssociatedModel->alias, array_keys($AssociatedModel->schema()));
                                                $result = array_merge($result, $_fields);
                                                continue;
                                        }

                                        if (strpos($fields[$i], '.') === false) {
                                                $this->_fieldMappings[$alias . '__' . $fields[$i]] = $alias . '.' . $fields[$i];
                                                $fieldName = $this->name($alias . '.' . $fields[$i]);
                                                $fieldAlias = $this->name($alias . '__' . $fields[$i]);
                                        } else {
                                                $build = explode('.', $fields[$i]);
                                                $build[0] = trim($build[0], '[]');
                                                $build[1] = trim($build[1], '[]');
                                                $name = $build[0] . '.' . $build[1];
                                                $alias = $build[0] . '__' . $build[1];

                                                $this->_fieldMappings[$alias] = $name;
                                                $fieldName = $this->name($name);
                                                $fieldAlias = $this->name($alias);
                                        }
                                        if ($model->getColumnType($fields[$i]) === 'datetime') {
                                                $fieldName = "CONVERT(VARCHAR(20), {$fieldName}, 20)";
                                        }
                                        $fields[$i] = "{$fieldName} AS {$fieldAlias}";
                                }
                                $result[] = $prepend . $fields[$i];
                        }
                        return $result;
                }
                return $fields;
        }

/**
 * Generates and executes an SQL INSERT statement for given model, fields, and values.
 * Removes Identity (primary key) column from update data before returning to parent, if
 * value is empty.
 *
 * @param Model $model The model to insert into.
 * @param array $fields The fields to set.
 * @param array $values The values to set.
 * @return array
 */
        public function create(Model $model, $fields = null, $values = null) {
                if (!empty($values)) {
                        $fields = array_combine($fields, $values);
                }
                $primaryKey = $this->_getPrimaryKey($model);

                if (array_key_exists($primaryKey, $fields)) {
                        if (empty($fields[$primaryKey])) {
                                unset($fields[$primaryKey]);
                        } else {
                                $this->_execute('SET IDENTITY_INSERT ' . $this->fullTableName($model) . ' ON');
                        }
                }
                $result = parent::create($model, array_keys($fields), array_values($fields));
                if (array_key_exists($primaryKey, $fields) && !empty($fields[$primaryKey])) {
                        $this->_execute('SET IDENTITY_INSERT ' . $this->fullTableName($model) . ' OFF');
                }
                return $result;
        }

/**
 * Generates and executes an SQL UPDATE statement for given model, fields, and values.
 * Removes Identity (primary key) column from update data before returning to parent.
 *
 * @param Model $model The model to update.
 * @param array $fields The fields to set.
 * @param array $values The values to set.
 * @param mixed $conditions The conditions to use.
 * @return array
 */
        public function update(Model $model, $fields = array(), $values = null, $conditions = null) {
                if (!empty($values)) {
                        $fields = array_combine($fields, $values);
                }
                if (isset($fields[$model->primaryKey])) {
                        unset($fields[$model->primaryKey]);
                }
                if (empty($fields)) {
                        return true;
                }
                return parent::update($model, array_keys($fields), array_values($fields), $conditions);
        }

/**
 * Returns a limit statement in the correct format for the particular database.
 *
 * @param int $limit Limit of results returned
 * @param int $offset Offset from which to start results
 * @return string SQL limit/offset statement
 */
        public function limit($limit, $offset = null) {
                if ($limit) {
                        $rt = '';
                        if (!strpos(strtolower($limit), 'top') || strpos(strtolower($limit), 'top') === 0) {
                                $rt = ' TOP';
                        }
                        $rt .= sprintf(' %u', $limit);
                        if (is_int($offset) && $offset > 0) {
                                $rt = sprintf(' OFFSET %u ROWS FETCH FIRST %u ROWS ONLY', $offset, $limit);
                        }
                        return $rt;
                }
                return null;
        }

/**
 * Converts database-layer column types to basic types
 *
 * @param mixed $real Either the string value of the fields type.
 *    or the Result object from Sqlserver::describe()
 * @return string Abstract column type (i.e. "string")
 */
        public function column($real) {
                $limit = null;
                $col = $real;
                if (is_object($real) && isset($real->Field)) {
                        $limit = $real->Length;
                        $col = $real->Type;
                }

                if ($col === 'datetime2') {
                        return 'datetime';
                }
                if (in_array($col, array('date', 'time', 'datetime', 'timestamp'))) {
                        return $col;
                }
                if ($col === 'bit') {
                        return 'boolean';
                }
                if (strpos($col, 'bigint') !== false) {
                        return 'biginteger';
                }
                if (strpos($col, 'int') !== false) {
                        return 'integer';
                }
                if (strpos($col, 'char') !== false && $limit == -1) {
                        return 'text';
                }
                if (strpos($col, 'char') !== false) {
                        return 'string';
                }
                if (strpos($col, 'text') !== false) {
                        return 'text';
                }
                if (strpos($col, 'binary') !== false || $col === 'image') {
                        return 'binary';
                }
                if (in_array($col, array('float', 'real'))) {
                        return 'float';
                }
                if (in_array($col, array('decimal', 'numeric'))) {
                        return 'decimal';
                }
                return 'text';
        }

/**
 * Handle SQLServer specific length properties.
 * SQLServer handles text types as nvarchar/varchar with a length of -1.
 *
 * @param mixed $length Either the length as a string, or a Column descriptor object.
 * @return mixed null|integer with length of column.
 */
        public function length($length) {
                if (is_object($length) && isset($length->Length)) {
                        if ($length->Length == -1 && strpos($length->Type, 'char') !== false) {
                                return null;
                        }
                        if (in_array($length->Type, array('nchar', 'nvarchar'))) {
                                return floor($length->Length / 2);
                        }
                        if ($length->Type === 'text') {
                                return null;
                        }
                        return $length->Length;
                }
                return parent::length($length);
        }

/**
 * Builds a map of the columns contained in a result
 *
 * @param PDOStatement $results The result to modify.
 * @return void
 */
        public function resultSet($results) {
                $this->map = array();
                $numFields = $results->columnCount();
                $index = 0;

                while ($numFields-- > 0) {
                        $column = $results->getColumnMeta($index);
                        $name = $column['name'];

                        if (strpos($name, '__')) {
                                if (isset($this->_fieldMappings[$name]) && strpos($this->_fieldMappings[$name], '.')) {
                                        $map = explode('.', $this->_fieldMappings[$name]);
                                } elseif (isset($this->_fieldMappings[$name])) {
                                        $map = array(0, $this->_fieldMappings[$name]);
                                } else {
                                        $map = array(0, $name);
                                }
                        } else {
                                $map = array(0, $name);
                        }
                        $map[] = ($column['sqlsrv:decl_type'] === 'bit') ? 'boolean' : $column['native_type'];
                        $this->map[$index++] = $map;
                }
        }

/**
 * Builds final SQL statement
 *
 * @param string $type Query type
 * @param array $data Query data
 * @return string
 */
        public function renderStatement($type, $data) {
                switch (strtolower($type)) {
                        case 'select':
                                extract($data);
                                $fields = trim($fields);

                                if (strpos($limit, 'TOP') !== false && strpos($fields, 'DISTINCT ') === 0) {
                                        $limit = 'DISTINCT ' . trim($limit);
                                        $fields = substr($fields, 9);
                                }

                                // hack order as SQLServer requires an order if there is a limit.
                                if ($limit && !$order) {
                                        $order = 'ORDER BY (SELECT NULL)';
                                }

                                // For older versions use the subquery version of pagination.
                                if (version_compare($this->getVersion(), '11', '<') && preg_match('/FETCH\sFIRST\s+([0-9]+)/i', $limit, $offset)) {
                                        preg_match('/OFFSET\s*(\d+)\s*.*?(\d+)\s*ROWS/', $limit, $limitOffset);

                                        $limit = 'TOP ' . (int)$limitOffset[2];
                                        $page = (int)($limitOffset[1] / $limitOffset[2]);
                                        $offset = (int)($limitOffset[2] * $page);

                                        $rowCounter = static::ROW_COUNTER;
                                        $sql = "SELECT {$limit} * FROM (
                                                        SELECT {$fields}, ROW_NUMBER() OVER ({$order}) AS {$rowCounter}
                                                        FROM {$table} {$alias} {$joins} {$conditions} {$group}
                                                ) AS _cake_paging_
                                                WHERE _cake_paging_.{$rowCounter} > {$offset}
                                                ORDER BY _cake_paging_.{$rowCounter}
                                        ";
                                        return trim($sql);
                                }
                                if (strpos($limit, 'FETCH') !== false) {
                                        return trim("SELECT {$fields} FROM {$table} {$alias} {$joins} {$conditions} {$group} {$order} {$limit}");
                                }
                                return trim("SELECT {$limit} {$fields} FROM {$table} {$alias} {$joins} {$conditions} {$group} {$order}");
                        case "schema":
                                extract($data);

                                foreach ($indexes as $i => $index) {
                                        if (preg_match('/PRIMARY KEY/', $index)) {
                                                unset($indexes[$i]);
                                                break;
                                        }
                                }

                                foreach (array('columns', 'indexes') as $var) {
                                        if (is_array(${$var})) {
                                                ${$var} = "\t" . implode(",\n\t", array_filter(${$var}));
                                        }
                                }
                                return trim("CREATE TABLE {$table} (\n{$columns});\n{$indexes}");
                        default:
                                return parent::renderStatement($type, $data);
                }
        }

/**
 * Returns a quoted and escaped string of $data for use in an SQL statement.
 *
 * @param string $data String to be prepared for use in an SQL statement
 * @param string $column The column into which this data will be inserted
 * @param bool $null Column allows NULL values
 * @return string Quoted and escaped data
 */
        public function value($data, $column = null, $null = true) {
                if ($data === null || is_array($data) || is_object($data)) {
                        return parent::value($data, $column, $null);
                }
                if (in_array($data, array('{$__cakeID__$}', '{$__cakeForeignKey__$}'), true)) {
                        return $data;
                }

                if (empty($column)) {
                        $column = $this->introspectType($data);
                }

                switch ($column) {
                        case 'string':
                        case 'text':
                                return 'N' . $this->_connection->quote($data, PDO::PARAM_STR);
                        default:
                                return parent::value($data, $column, $null);
                }
        }

/**
 * Returns an array of all result rows for a given SQL query.
 * Returns false if no rows matched.
 *
 * @param Model $model The model to read from
 * @param array $queryData The query data
 * @param int $recursive How many layers to go.
 * @return array|false Array of resultset rows, or false if no rows matched
 */
        public function read(Model $model, $queryData = array(), $recursive = null) {
                $results = parent::read($model, $queryData, $recursive);
                $this->_fieldMappings = array();
                return $results;
        }

/**
 * Fetches the next row from the current result set.
 * Eats the magic ROW_COUNTER variable.
 *
 * @return mixed
 */
        public function fetchResult() {
                if ($row = $this->_result->fetch(PDO::FETCH_NUM)) {
                        $resultRow = array();
                        foreach ($this->map as $col => $meta) {
                                list($table, $column, $type) = $meta;
                                if ($table === 0 && $column === static::ROW_COUNTER) {
                                        continue;
                                }
                                $resultRow[$table][$column] = $row[$col];
                                if ($type === 'boolean' && $row[$col] !== null) {
                                        $resultRow[$table][$column] = $this->boolean($resultRow[$table][$column]);
                                }
                        }
                        return $resultRow;
                }
                $this->_result->closeCursor();
                return false;
        }

/**
 * Inserts multiple values into a table
 *
 * @param string $table The table to insert into.
 * @param string $fields The fields to set.
 * @param array $values The values to set.
 * @return void
 */
        public function insertMulti($table, $fields, $values) {
                $primaryKey = $this->_getPrimaryKey($table);
                $hasPrimaryKey = $primaryKey && (
                        (is_array($fields) && in_array($primaryKey, $fields)
                        || (is_string($fields) && strpos($fields, $this->startQuote . $primaryKey . $this->endQuote) !== false))
                );

                if ($hasPrimaryKey) {
                        $this->_execute('SET IDENTITY_INSERT ' . $this->fullTableName($table) . ' ON');
                }

                parent::insertMulti($table, $fields, $values);

                if ($hasPrimaryKey) {
                        $this->_execute('SET IDENTITY_INSERT ' . $this->fullTableName($table) . ' OFF');
                }
        }

/**
 * Generate a database-native column schema string
 *
 * @param array $column An array structured like the
 *   following: array('name'=>'value', 'type'=>'value'[, options]),
 *   where options can be 'default', 'length', or 'key'.
 * @return string
 */
        public function buildColumn($column) {
                $result = parent::buildColumn($column);
                $result = preg_replace('/(bigint|int|integer)\([0-9]+\)/i', '$1', $result);
                $result = preg_replace('/(bit)\([0-9]+\)/i', '$1', $result);
                if (strpos($result, 'DEFAULT NULL') !== false) {
                        if (isset($column['default']) && $column['default'] === '') {
                                $result = str_replace('DEFAULT NULL', "DEFAULT ''", $result);
                        } else {
                                $result = str_replace('DEFAULT NULL', 'NULL', $result);
                        }
                } elseif (array_keys($column) === array('type', 'name')) {
                        $result .= ' NULL';
                } elseif (strpos($result, "DEFAULT N'")) {
                        $result = str_replace("DEFAULT N'", "DEFAULT '", $result);
                }
                return $result;
        }

/**
 * Format indexes for create table
 *
 * @param array $indexes The indexes to build
 * @param string $table The table to make indexes for.
 * @return string
 */
        public function buildIndex($indexes, $table = null) {
                $join = array();

                foreach ($indexes as $name => $value) {
                        if ($name === 'PRIMARY') {
                                $join[] = 'PRIMARY KEY (' . $this->name($value['column']) . ')';
                        } elseif (isset($value['unique']) && $value['unique']) {
                                $out = "ALTER TABLE {$table} ADD CONSTRAINT {$name} UNIQUE";

                                if (is_array($value['column'])) {
                                        $value['column'] = implode(', ', array_map(array(&$this, 'name'), $value['column']));
                                } else {
                                        $value['column'] = $this->name($value['column']);
                                }
                                $out .= "({$value['column']});";
                                $join[] = $out;
                        }
                }
                return $join;
        }

/**
 * Makes sure it will return the primary key
 *
 * @param Model|string $model Model instance of table name
 * @return string
 */
        protected function _getPrimaryKey($model) {
                $schema = $this->describe($model);
                foreach ($schema as $field => $props) {
                        if (isset($props['key']) && $props['key'] === 'primary') {
                                return $field;
                        }
                }
                return null;
        }

/**
 * Returns number of affected rows in previous database operation. If no previous operation exists,
 * this returns false.
 *
 * @param mixed $source Unused
 * @return int Number of affected rows
 */
        public function lastAffected($source = null) {
                $affected = parent::lastAffected();
                if ($affected === null && $this->_lastAffected !== false) {
                        return $this->_lastAffected;
                }
                return $affected;
        }

/**
 * Executes given SQL statement.
 *
 * @param string $sql SQL statement
 * @param array $params list of params to be bound to query (supported only in select)
 * @param array $prepareOptions Options to be used in the prepare statement
 * @return mixed PDOStatement if query executes with no problem, true as the result of a successful, false on error
 * query returning no rows, such as a CREATE statement, false otherwise
 * @throws PDOException
 */
        protected function _execute($sql, $params = array(), $prepareOptions = array()) {
                $this->_lastAffected = false;
                $sql = trim($sql);
                if (strncasecmp($sql, 'SELECT', 6) === 0 || preg_match('/^EXEC(?:UTE)?\s/mi', $sql) > 0) {
                        $prepareOptions += array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL);
                        return parent::_execute($sql, $params, $prepareOptions);
                }
                try {
                        $this->_lastAffected = $this->_connection->exec($sql);
                        if ($this->_lastAffected === false) {
                                $this->_results = null;
                                $error = $this->_connection->errorInfo();
                                $this->error = $error[2];
                                return false;
                        }
                        return true;
                } catch (PDOException $e) {
                        if (isset($query->queryString)) {
                                $e->queryString = $query->queryString;
                        } else {
                                $e->queryString = $sql;
                        }
                        throw $e;
                }
        }

/**
 * Generate a "drop table" statement for the given table
 *
 * @param type $table Name of the table to drop
 * @return string Drop table SQL statement
 */
        protected function _dropTable($table) {
                return "IF OBJECT_ID('" . $this->fullTableName($table, false) . "', 'U') IS NOT NULL DROP TABLE " . $this->fullTableName($table) . ";";
        }

/**
 * Gets the schema name
 *
 * @return string The schema name
 */
        public function getSchemaName() {
                return $this->config['schema'];
        }

}