Think/Model.php
public function query($sql)
    {
        $sql = $this->parseSql($sql);

        return $this->db->query($sql);
    }
public function query($sql)
    {
        $sql = $this->parseSql($sql);

        return $this->db->query($sql);
    }
SQL查询
@param string $sql SQL指令
@return mixed