Hi, Actually we do not have "last" syntax now. There are two ways to treat last:
(1) Treat it as a special case of raw data query (2)Treat it as a aggregation query Before deciding, let's consider two questions: (1) Is last an aggregation function or is the result format of last the same with aggregation queries? I thinks it's not. One aggregation function should return one column. For example, the result of "select count(s1) from xx" has one column: count(s1). However, the last should return three columns: path, time, value (2) Could "last" be used with other aggregations at the same time? NO, if users issue a last query, he should query the last of all selected series. "select last(s1), count(s2)" is not allowed. i.e., it could only be this form: select last(s1), last(s2), last(s3), last(s4) from root.sg.d1. And if so, why we duplicate last so many times... Therefor, I prefer treat last as a special case of raw data query. i.e., 4. select last s1, s2 from root.sg.d1 Thanks, -- Jialin Qiao School of Software, Tsinghua University 乔嘉林 清华大学 软件学院 > -----原始邮件----- > 发件人: "Xiangdong Huang" <[email protected]> > 发送时间: 2020-02-21 19:44:46 (星期五) > 收件人: [email protected] > 抄送: > 主题: Re: Last Query syntax vote > > Hi, > > +1 for select last(s1), last(s2) from root.sg.d > > I think this vote description does not show why we need a new syntax and > the data result format we will get... > > For example, the first SQL is a common query statement, but why it is not > suitable and you want a new syntax? > > It is hard to let other guys joining the vote. > > Best, > ----------------------------------- > Xiangdong Huang > School of Software, Tsinghua University > > 黄向东 > 清华大学 软件学院 > > > Dawei Liu <[email protected]> 于2020年2月21日周五 下午5:35写道： > > > Hi, > > > > I’d vote for > > > > [2] select last(s1), last(s2) from root.sg.d align by sensor > > > > It looks simple, it's easy to use, it's human logic > > > > > > Thanks > > --- > > Dawei Liu > > > > > > > > > 2020年2月21日 下午5:26，Wei Shao <[email protected]> 写道： > > > > > > Hi, > > > > > > > > > I'd vote for > > > [4]. select last s1, s2 from root.sg.d > > > > > > > > > Thanks, > > > Wei > > > > > > > > > > > > At 2020-02-21 17:08:14, "Wei Shao" <[email protected]> wrote: > > >> Hi, > > >> > > >> > > >> We are to determine the exact syntax of Last Query for IoTDB. Last > > query is to select the latest time-value pair result for a given timeseries. > > >> You can choose from the following syntax options. > > >> 1. select last(s1), last(s2) from root.sg.d > > >> 2. select last(s1), last(s2) from root.sg.d align by sensor > > >> 3. select last(s1, s2) from root.sg.d > > >> 4. select last s1, s2 from root.sg.d > > >> 5. last s1, s2 from root.sg.d > > >> 6. select s1, s2 from root.sg.d last > > >> 7. select s1, s2 from root.sg.d onlylast > > >> > > >> > > >> Please vote for the option you are comfortable with. > > >> > > >> > > >> Thanks, > > >> Wei > > > >
