public function buildSelectQuery($table, $cols, $where, $limit, $order, $group) {      
        return "SELECT $cols FROM {$this->prefix}$table" . 
               ($where ? " WHERE $where" : '') .
               ($group ? " GROUP BY $group" : '') .
               ($order ? " ORDER BY $order" : '') . 
               ($limit ? " LIMIT $limit" : '') . ';'; 
    }

    public function select($table, $cols = '*', $where = null) {
        $query = $this->buildSelectQuery($table, $cols, $where);
        $result = $this->query($query);
        return $this->fetch($result);
    }
    
    public function find($table, $id, $cols = '*') {
        return $this->select($table, $cols, 'id = ' . intval($id));
    }
    
    public function selectAll($table, $cols = '*', $where = null, $limit = null, $order = null, $group = null) {
        $query = $this->buildSelectQuery($table, $cols, $where, $limit, $order, $group);
        $result = $this->query($query);
        return $this->fetchAll($result);
    }
    
    public function search($table, $cols, $key_col, $text, $limit = null, $order = null) {
        return $this->selectAll($table, $cols, "$key_col LIKE '%" . $this->escapeLike($text) . "%'", $limit, $order);
    }
    
    public function fullTextSearch($table, $cols, $match_cols, $text, $limit = null, $order = null) {
        return $this->selectAll($table, $cols, "MATCH ($match_cols) AGAINST (" . $this->quote($text) . ')', $limit, $order);
    }

/**
     * Получить значения из таблицы как ассоциативный массив.
     */
    public function assoc($table, $key_field, $value_field, $where = null) {
        $result = $this->query($this->buildSelectQuery($table, "$key_field, $value_field", $where));
        $keys = $this->fetchCol($result, $key_field);
        if (empty($keys)) {
            return $keys;
        }
        $this->seek($result); // сбросили указатель
        $values = $this->fetchCol($result, $value_field);
        return array_combine($keys, $values);
    }
    
    public function assocId($table, $field, $where = null) {
        return $this->assoc($table, 'id', $field, $where);
    }

    /**
     * Посчитать количество рядов в таблице.
     */
    public function count($table, $field, $where = null) {
        $result = $this->query($this->buildSelectQuery($table, "COUNT($field)", $where));
        return (int) $this->single($result);
    }
    
    /**
     * Посчитать количество всех рядов в таблице.
     */
    public function countAll($table, $where = null) {
        return $this->count($table, '*', $where);
    }
    
    /**
     * Посчитать количество рядов с уникальными значениями стобца $field в таблице.
     */
    public function countUnique($table, $field, $where = null) {
        return $this->count($table, "DISTINCT $field", $where);
    }

    public function quote($string) {
        return "'" . $this->escape($string) . "'";
    }
    
    public function escapeLike($string) {
        $string = $this->escape($string);
        $string = str_replace(array('%', '_'), array('\%', '\_'), $string);
        return $string;
    }  

    private function _prepare(&$data) {
        foreach ($data as &$v) {
            if (is_null($v)) {
                $v = 'NULL';
            }
            else if (is_bool($v)) {
                $v = $v ? 'TRUE' : 'FALSE';
            }
            else if (is_string($v)) {
                $v = $this->quote($v);
            }
        }
    }
    
    public function insert($table, $data) {
        $this->_prepare($data);
        $query = "INSERT INTO {$this->prefix}$table";
        $query .= ' (' . implode(', ', array_keys($data)) . ')';
        $query .= ' VALUES (' . implode(', ', array_values($data)) . ');';
        $this->query($query);
        return $this->insertId();
    }

    public function query($query) {
        ++$this->counter;
        $this->executionTime = -microtime(1);
        $result = mysql_query($query, $this->_connection);
        $this->executionTime += microtime(1);
        $this->totalExecutionTime += $this->executionTime;
        $this->numRows = null;
        $this->affectedRows = mysql_affected_rows($this->_connection);
        
        if (is_bool($result)) {
            if (!$result) {
                throw new Exception('SQL Error Code: ' . mysql_errno($this->_connection) . ' - ' . mysql_error($this->_connection) . ". Query: $query");
            }
        }
        else {
            // $this->numRows = mysql_num_rows($result);
            $this->numRows = $this->affectedRows;   
            return $result;
        }       
    }

$this->_connection

$db->insert('users', array('id' => null, 'name' => 'tester', 'pass' => 'qwerty', 'reg_dateime' => 'DATETIME'));

INSERT INTO t_users (id, name, pass, reg_dateime) VALUES (NULL, 'tester', 'qwerty', 'DATETIME');