public function toSql()
{
return implode(' ', array_filter(array($this->_clause($this->_distinct ? 'SELECT DISTINCT' : 'SELECT', $this->_select), $this->_clause('FROM', $this->_from), implode(' ', $this->_joins), $this->_clause('WHERE', $this->_where), $this->_clause('GROUP BY', $this->_group), $this->_clause('ORDER BY', $this->_order), $this->_limit, $this->_lock)));
}