<?php

/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * 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 license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Db
 * @subpackage Select
 * @copyright  Copyright (c) 2005-2007 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: Select.php 163 2008-01-14 04:40:16Z matt $
 */


/**
 * @see Zend_Db_Adapter_Abstract
 */
require_once 'Zend/Db/Adapter/Abstract.php';

/**
 * @see Zend_Db_Expr
 */
require_once 'Zend/Db/Expr.php';


/**
 * Class for SQL SELECT generation and results.
 *
 * @category   Zend
 * @package    Zend_Db
 * @subpackage Select
 * @copyright  Copyright (c) 2005-2007 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Db_Select
{

    const DISTINCT     = 'distinct';
    const FOR_UPDATE   = 'forupdate';
    const COLUMNS      = 'columns';
    const FROM         = 'from';
    const WHERE        = 'where';
    const GROUP        = 'group';
    const HAVING       = 'having';
    const ORDER        = 'order';
    const LIMIT_COUNT  = 'limitcount';
    const LIMIT_OFFSET = 'limitoffset';

    const INNER_JOIN   = 'inner join';
    const LEFT_JOIN    = 'left join';
    const RIGHT_JOIN   = 'right join';
    const FULL_JOIN    = 'full join';
    const CROSS_JOIN   = 'cross join';
    const NATURAL_JOIN = 'natural join';

    /**
     * Zend_Db_Adapter_Abstract object.
     *
     * @var Zend_Db_Adapter_Abstract
     */
    protected $_adapter;

    /**
     * The initial values for the $_parts array.
     *
     * @var array
     */
    protected static $_partsInit = array(
        self::DISTINCT     => false,
        self::FOR_UPDATE   => false,
        self::COLUMNS      => array(),
        self::FROM         => array(),
        self::WHERE        => array(),
        self::GROUP        => array(),
        self::HAVING       => array(),
        self::ORDER        => array(),
        self::LIMIT_COUNT  => null,
        self::LIMIT_OFFSET => null,
    );

    /**
     * The component parts of a SELECT statement.
     * Initialized to the $_partsInit array in the constructor.
     *
     * @var array
     */
    protected $_parts = array();

    /**
     * Tracks which columns are being select from each table and join.
     *
     * @var array
     */
    protected $_tableCols = array();

    /**
     * Class constructor
     *
     * @param Zend_Db_Adapter_Abstract $adapter
     */
    public function __construct(Zend_Db_Adapter_Abstract $adapter)
    {
        $this->_adapter = $adapter;
        $this->_parts = self::$_partsInit;
    }

    /**
     * Converts this object to an SQL SELECT string.
     *
     * @return string This object as a SELECT string.
     */
    public function __toString()
    {
        // initial SELECT [DISTINCT] [FOR UPDATE]
        $sql = 'SELECT';
        if ($this->_parts[self::DISTINCT]) {
            $sql .= ' DISTINCT';
        }
        if ($this->_parts[self::FOR_UPDATE]) {
            $sql .= ' FOR UPDATE';
        }
        $sql .= "\n\t";

        // add columns
        $columns = array();
        foreach ($this->_parts[self::COLUMNS] as $columnEntry) {
            list($correlationName, $column, $alias) = $columnEntry;
            if ($column instanceof Zend_Db_Expr) {
                $columns[] = $this->_adapter->quoteColumnAs($column, $alias, true);
            } else {
                if ($column == '*') {
                    $column = new Zend_Db_Expr('*');
                    $alias = null;
                }
                if (empty($correlationName)) {
                    $columns[] = $this->_adapter->quoteColumnAs($column, $alias, true);
                } else {
                    $columns[] = $this->_adapter->quoteColumnAs(array($correlationName, $column), $alias, true);
                }
            }
        }
        $sql .= implode(",\n\t", $columns);

        // from these joined tables
        if ($this->_parts[self::FROM]) {
            $from = array();
            foreach ($this->_parts[self::FROM] as $correlationName => $table) {
                $tmp = '';
                if (empty($from)) {
                    // Add schema if available
                    if (null !== $table['schema']) {
                        $tmp .= $this->_adapter->quoteIdentifier($table['schema'], true) . '.';
                    }
                    // First table is named alone ignoring join information
                    $tmp .= $this->_adapter->quoteTableAs($table['tableName'], $correlationName, true);
                } else {
                    // Subsequent tables may have joins
                    if (! empty($table['joinType'])) {
                        $tmp .= ' ' . strtoupper($table['joinType']) . ' ';
                    }
                    // Add schema if available
                    if (null !== $table['schema']) {
                        $tmp .= $this->_adapter->quoteIdentifier($table['schema'], true) . '.';
                    }
                    $tmp .= $this->_adapter->quoteTableAs($table['tableName'], $correlationName, true);
                    if (! empty($table['joinCondition'])) {
                        $tmp .= ' ON ' . $table['joinCondition'];
                    }
                }
                // add the table name and condition
                // add to the list
                $from[] = $tmp;
            }
            // add the list of all joins
            if (!empty($from)) {
                $sql .= "\nFROM " . implode("\n", $from);
            }

            // with these where conditions
            if ($this->_parts[self::WHERE]) {
                $sql .= "\nWHERE\n\t";
                $sql .= implode("\n\t", $this->_parts[self::WHERE]);
            }

            // grouped by these columns
            if ($this->_parts[self::GROUP]) {
                $sql .= "\nGROUP BY\n\t";
                $l = array();
                foreach ($this->_parts[self::GROUP] as $term) {
                    $l[] = $this->_adapter->quoteIdentifier($term, true);
                }
                $sql .= implode(",\n\t", $l);
            }

            // having these conditions
            if ($this->_parts[self::HAVING]) {
                $sql .= "\nHAVING\n\t";
                $sql .= implode("\n\t", $this->_parts[self::HAVING]);
            }

        }

        // ordered by these columns
        if ($this->_parts[self::ORDER]) {
            $sql .= "\nORDER BY\n\t";
            $l = array();
            foreach ($this->_parts[self::ORDER] as $term) {
                if (is_array($term)) {
                    $l[] = $this->_adapter->quoteIdentifier($term[0], true) . ' ' . $term[1];
                } else {
                    $l[] = $this->_adapter->quoteIdentifier($term, true);
                }
            }
            $sql .= implode(",\n\t", $l);
        }

        // determine offset
        $count = 0;
        $offset = 0;
        if (!empty($this->_parts[self::LIMIT_OFFSET])) {
            $offset = (int) $this->_parts[self::LIMIT_OFFSET];
            // this should be reduced to the max integer PHP can support
            $count = intval(9223372036854775807);
        }

        // determine count
        if (!empty($this->_parts[self::LIMIT_COUNT])) {
            $count = (int) $this->_parts[self::LIMIT_COUNT];
        }

        // add limits clause
        if ($count > 0) {
            $sql .= "\n";
            $sql = trim($this->_adapter->limit($sql, $count, $offset));
        }

        return $sql;
    }

    /**
     * Makes the query SELECT DISTINCT.
     *
     * @param bool $flag Whether or not the SELECT is DISTINCT (default true).
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function distinct($flag = true)
    {
        $this->_parts[self::DISTINCT] = (bool) $flag;
        return $this;
    }

    /**
     * Makes the query SELECT FOR UPDATE.
     *
     * @param bool $flag Whether or not the SELECT is FOR UPDATE (default true).
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function forUpdate($flag = true)
    {
        $this->_parts[self::FOR_UPDATE] = (bool) $flag;
        return $this;
    }

    /**
     * Adds a FROM table and optional columns to the query.
     *
     * The first parameter $name can be a simple string, in which case the
     * correlation name is generated automatically.  If you want to specify
     * the correlation name, the first parameter must be an associative
     * array in which the key is the physical table name, and the value is
     * the correlation name.  For example, array('table' => 'alias').
     * The correlation name is prepended to all columns fetched for this
     * table.
     *
     * The second parameter can be a single string or Zend_Db_Expr object,
     * or else an array of strings or Zend_Db_Expr objects.
     *
     * The first parameter can be null or an empty string, in which case
     * no correlation name is generated or prepended to the columns named
     * in the second parameter.
     *
     * @param  array|string|Zend_Db_Expr $name The table name or an associative array relating table name to
     *                                         correlation name.
     * @param  array|string|Zend_Db_Expr $cols The columns to select from this table.
     * @param  string $schema The schema name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function from($name, $cols = '*', $schema = null)
    {
        return $this->joinInner($name, null, $cols, $schema);
    }

    /**
     * Populate the {@link $_parts} 'join' key
     *
     * Does the dirty work of populating the join key.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  null|string $type Type of join; inner, left, and null are currently supported
     * @param  array|string|Zend_Db_Expr $name Table name
     * @param  string $cond Join on this condition
     * @param  array|string $cols The columns to select from the joined table
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object
     * @throws Zend_Db_Select_Exception
     */
    protected function _join($type, $name, $cond, $cols, $schema = null)
    {
        $joinTypes = array(self::INNER_JOIN, self::LEFT_JOIN, self::RIGHT_JOIN, self::FULL_JOIN, self::CROSS_JOIN, self::NATURAL_JOIN);
        if (!in_array($type, $joinTypes)) {
            /**
             * @see Zend_Db_Select_Exception
             */
            require_once 'Zend/Db/Select/Exception.php';
            throw new Zend_Db_Select_Exception("Invalid join type '$type'");
        }

        if (empty($name)) {
            $correlationName = $tableName = '';
        } else if (is_array($name)) {
            // Must be array($correlationName => $tableName) or array($ident, ...)
            foreach ($name as $_correlationName => $_tableName) {
                if (is_string($_correlationName)) {
                    // We assume the key is the correlation name and value is the table name
                    $tableName = $_tableName;
                    $correlationName = $_correlationName;
                } else {
                    // We assume just an array of identifiers, with no correlation name
                    $tableName = $name;
                    $correlationName = $this->_uniqueCorrelation($tableName);
                }
                break;
            }
        } else if ($name instanceof Zend_Db_Expr) {
            $tableName = $name;
            $correlationName = $this->_uniqueCorrelation('t');
        } else if (preg_match('/^(.+)\s+AS\s+(.+)$/i', $name, $m)) {
            $tableName = $m[1];
            $correlationName = $m[2];
        } else {
            $tableName = $name;
            $correlationName = $this->_uniqueCorrelation($tableName);
        }

        // Schema from table name overrides schema argument
        if (false !== strpos($tableName, '.')) {
            list($schema, $tableName) = explode('.', $tableName);
        }

        if (!empty($correlationName)) {
            if (array_key_exists($correlationName, $this->_parts[self::FROM])) {
                /**
                 * @see Zend_Db_Select_Exception
                 */
                require_once 'Zend/Db/Select/Exception.php';
                throw new Zend_Db_Select_Exception("You cannot define a correlation name '$correlationName' more than once");
            }

            $this->_parts[self::FROM][$correlationName] = array(
                'joinType'      => $type,
                'schema'        => $schema,
                'tableName'     => $tableName,
                'joinCondition' => $cond
            );
        }

        // add to the columns from this joined table
        $this->_tableCols($correlationName, $cols);

        return $this;
    }

    /**
     * Generate a unique correlation name
     *
     * @param string|array $name A qualified identifier.
     * @return string A unique correlation name.
     */
    private function _uniqueCorrelation($name)
    {
        if (is_array($name)) {
            $c = end($name);
        } else {
            // Extract just the last name of a qualified table name
            $dot = strrpos($name,'.');
            $c = ($dot === false) ? $name : substr($name, $dot+1);
        }
        for ($i = 2; array_key_exists($c, $this->_parts[self::FROM]); ++$i) {
            $c = $name . '_' . (string) $i;
        }
        return $c;
    }

    /**
     * Adds a JOIN table and columns to the query.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  string $cond Join on this condition.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function join($name, $cond, $cols = '*', $schema = null)
    {
        return $this->joinInner($name, $cond, $cols);
    }

    /**
     * Add an INNER JOIN table and colums to the query
     * Rows in both tables are matched according to the expression
     * in the $cond argument.  The result set is comprised
     * of all cases where rows from the left table match
     * rows from the right table.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  string $cond Join on this condition.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinInner($name, $cond, $cols = '*', $schema = null)
    {
        return $this->_join(self::INNER_JOIN, $name, $cond, $cols, $schema);
    }

    /**
     * Add a LEFT OUTER JOIN table and colums to the query
     * All rows from the left operand table are included,
     * matching rows from the right operand table included,
     * and the columns from the right operand table are filled
     * with NULLs if no row exists matching the left table.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  string $cond Join on this condition.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinLeft($name, $cond, $cols = '*', $schema = null)
    {
        return $this->_join(self::LEFT_JOIN, $name, $cond, $cols, $schema);
    }

    /**
     * Add a RIGHT OUTER JOIN table and colums to the query.
     * Right outer join is the complement of left outer join.
     * All rows from the right operand table are included,
     * matching rows from the left operand table included,
     * and the columns from the left operand table are filled
     * with NULLs if no row exists matching the right table.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  string $cond Join on this condition.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinRight($name, $cond, $cols = '*', $schema = null)
    {
        return $this->_join(self::RIGHT_JOIN, $name, $cond, $cols, $schema);
    }

    /**
     * Add a FULL OUTER JOIN table and colums to the query.
     * A full outer join is like combining a left outer join
     * and a right outer join.  All rows from both tables are
     * included, paired with each other on the same row of the
     * result set if they satisfy the join condition, and otherwise
     * paired with NULLs in place of columns from the other table.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  string $cond Join on this condition.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinFull($name, $cond, $cols = '*', $schema = null)
    {
        return $this->_join(self::FULL_JOIN, $name, $cond, $cols, $schema);
    }

    /**
     * Add a CROSS JOIN table and colums to the query.
     * A cross join is a cartesian product; there is no join condition.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinCross($name, $cols = '*', $schema = null)
    {
        return $this->_join(self::CROSS_JOIN, $name, null, $cols, $schema);
    }

    /**
     * Add a NATURAL JOIN table and colums to the query.
     * A natural join assumes an equi-join across any column(s)
     * that appear with the same name in both tables.
     * Only natural inner joins are supported by this API,
     * even though SQL permits natural outer joins as well.
     *
     * The $name and $cols parameters follow the same logic
     * as described in the from() method.
     *
     * @param  array|string|Zend_Db_Expr $name The table name.
     * @param  array|string $cols The columns to select from the joined table.
     * @param  string $schema The database name to specify, if any.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function joinNatural($name, $cols = '*', $schema = null)
    {
        return $this->_join(self::NATURAL_JOIN, $name, null, $cols, $schema);
    }

    /**
     * Adds a WHERE condition to the query by AND.
     *
     * If a value is passed as the second param, it will be quoted
     * and replaced into the condition wherever a question-mark
     * appears. Array values are quoted and comma-separated.
     *
     * <code>
     * // simplest but non-secure
     * $select->where("id = $id");
     *
     * // secure (ID is quoted but matched anyway)
     * $select->where('id = ?', $id);
     *
     * // alternatively, with named binding
     * $select->where('id = :id');
     * </code>
     *
     * Note that it is more correct to use named bindings in your
     * queries for values other than strings. When you use named
     * bindings, don't forget to pass the values when actually
     * making a query:
     *
     * <code>
     * $db->fetchAll($select, array('id' => 5));
     * </code>
     *
     * @param string $cond The WHERE condition.
     * @param string $val A single value to quote into the condition.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function where($cond)
    {
        if (func_num_args() > 1) {
            $val = func_get_arg(1);
            $cond = $this->_adapter->quoteInto($cond, $val);
        }

        if ($this->_parts[self::WHERE]) {
            $this->_parts[self::WHERE][] = "AND ($cond)";
        } else {
            $this->_parts[self::WHERE][] = "($cond)";
        }

        return $this;
    }

    /**
     * Adds a WHERE condition to the query by OR.
     *
     * Otherwise identical to where().
     *
     * @param string $cond The WHERE condition.
     * @param string $val A value to quote into the condition.
     * @return Zend_Db_Select This Zend_Db_Select object.
     *
     * @see where()
     */
    public function orWhere($cond)
    {
        if (func_num_args() > 1) {
            $val = func_get_arg(1);
            $cond = $this->_adapter->quoteInto($cond, $val);
        }

        if ($this->_parts[self::WHERE]) {
            $this->_parts[self::WHERE][] = "OR ($cond)";
        } else {
            $this->_parts[self::WHERE][] = "($cond)";
        }

        return $this;
    }

    /**
     * Adds grouping to the query.
     *
     * @param  array|string $spec The column(s) to group by.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function group($spec)
    {
        if (!is_array($spec)) {
            $spec = array($spec);
        }

        foreach ($spec as $val) {
            if (preg_match('/\(.*\)/', (string) $val)) {
                $val = new Zend_Db_Expr($val);
            }
            $this->_parts[self::GROUP][] = $val;
        }

        return $this;
    }

    /**
     * Adds a HAVING condition to the query by AND.
     *
     * If a value is passed as the second param, it will be quoted
     * and replaced into the condition wherever a question-mark
     * appears. See {@link where()} for an example
     *
     * @param string $cond The HAVING condition.
     * @param string|Zend_Db_Expr $val A single value to quote into the condition.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function having($cond)
    {
        if (func_num_args() > 1) {
            $val = func_get_arg(1);
            $cond = $this->_adapter->quoteInto($cond, $val);
        }

        if ($this->_parts[self::HAVING]) {
            $this->_parts[self::HAVING][] = "AND ($cond)";
        } else {
            $this->_parts[self::HAVING][] = "($cond)";
        }

        return $this;
    }

    /**
     * Adds a HAVING condition to the query by OR.
     *
     * Otherwise identical to orHaving().
     *
     * @param string $cond The HAVING condition.
     * @param string $val A single value to quote into the condition.
     * @return Zend_Db_Select This Zend_Db_Select object.
     *
     * @see having()
     */
    public function orHaving($cond)
    {
        if (func_num_args() > 1) {
            $val = func_get_arg(1);
            $cond = $this->_adapter->quoteInto($cond, $val);
        }

        if ($this->_parts[self::HAVING]) {
            $this->_parts[self::HAVING][] = "OR ($cond)";
        } else {
            $this->_parts[self::HAVING][] = "($cond)";
        }

        return $this;
    }

    /**
     * Adds a row order to the query.
     *
     * @param mixed $spec The column(s) and direction to order by.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function order($spec)
    {
        if (!is_array($spec)) {
            $spec = array($spec);
        }

        // force 'ASC' or 'DESC' on each order spec, default is ASC.
        foreach ($spec as $val) {
            if ($val instanceof Zend_Db_Expr) {
                $expr = $val->__toString();
                if (empty($expr)) {
                    continue;
                }
                $this->_parts[self::ORDER][] = $val;
            } else {
                if (empty($val)) {
                    continue;
                }
                $direction = 'ASC';
                if (preg_match('/(.*)\s+(ASC|DESC)\s*$/i', $val, $matches)) {
                    $val = trim($matches[1]);
                    $direction = $matches[2];
                }
                if (preg_match('/\(.*\)/', $val)) {
                    $val = new Zend_Db_Expr($val);
                }
                $this->_parts[self::ORDER][] = array($val, $direction);
            }
        }

        return $this;
    }

    /**
     * Sets a limit count and offset to the query.
     *
     * @param int $count OPTIONAL The number of rows to return.
     * @param int $offset OPTIONAL Start returning after this many rows.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function limit($count = null, $offset = null)
    {
        $this->_parts[self::LIMIT_COUNT]  = (int) $count;
        $this->_parts[self::LIMIT_OFFSET] = (int) $offset;
        return $this;
    }

    /**
     * Sets the limit and count by page number.
     *
     * @param int $page Limit results to this page number.
     * @param int $rowCount Use this many rows per page.
     * @return Zend_Db_Select This Zend_Db_Select object.
     */
    public function limitPage($page, $rowCount)
    {
        $page     = ($page > 0)     ? $page     : 1;
        $rowCount = ($rowCount > 0) ? $rowCount : 1;
        $this->_parts[self::LIMIT_COUNT]  = (int) $rowCount;
        $this->_parts[self::LIMIT_OFFSET] = (int) $rowCount * ($page - 1);
        return $this;
    }

    /**
     * Adds to the internal table-to-column mapping array.
     *
     * @param  string $tbl The table/join the columns come from.
     * @param  array|string $cols The list of columns; preferably as
     * an array, but possibly as a string containing one column.
     * @return void
     */
    protected function _tableCols($correlationName, $cols)
    {
        if (!is_array($cols)) {
            $cols = array($cols);
        }
        if ($correlationName == null) {
            $correlationName = '';
        }

        foreach ($cols as $alias => $col) {
            $currentCorrelationName = $correlationName;
            if (is_string($col)) {
                // Check for a column matching "<column> AS <alias>" and extract the alias name
                if (preg_match('/^(.+)\s+AS\s+(.+)$/i', $col, $m)) {
                    $col = $m[1];
                    $alias = $m[2];
                }
                // Check for columns that look like functions and convert to Zend_Db_Expr
                if (preg_match('/\(.*\)/', $col)) {
                    $col = new Zend_Db_Expr($col);
                } elseif (preg_match('/(.+)\.(.+)/', $col, $m)) {
                    $currentCorrelationName = $m[1];
                    $col = $m[2];
                }
            }
            $this->_parts[self::COLUMNS][] = array($currentCorrelationName, $col, is_string($alias) ? $alias : null);
        }
    }

    /**
     * Get part of the structured information for the currect query.
     *
     * @param string $part
     * @return mixed
     * @throws Zend_Db_Select_Exception
     */
    public function getPart($part)
    {
        $part = strtolower($part);
        if (!array_key_exists($part, $this->_parts)) {
            /**
             * @see Zend_Db_Select_Exception
             */
            require_once 'Zend/Db/Select/Exception.php';
            throw new Zend_Db_Select_Exception("Invalid Select part '$part'");
        }
        return $this->_parts[ $part ];
    }

    /**
     * @param integer $fetchMode OPTIONAL
     * @return PDO_Statement|Zend_Db_Statement
     */
    public function query($fetchMode = null)
    {
        $stmt = $this->_adapter->query($this);
        if ($fetchMode == null) {
            $fetchMode = $this->_adapter->getFetchMode();
        }
        $stmt->setFetchMode($fetchMode);
        return $stmt;
    }

    /**
     * Clear parts of the Select object, or an individual part.
     *
     * @param string $part OPTIONAL
     * @return Zend_Db_Select
     */
    public function reset($part = null)
    {
        if ($part == null) {
            $this->_parts = self::$_partsInit;
        } else if (array_key_exists($part, self::$_partsInit)) {
            $this->_parts[$part] = self::$_partsInit[$part];
        }
        return $this;
    }

}
