Hi, The term "group by device" is fine for ok.
Or, we can I think classify the queries into 3 part: 1. return data points time series by time series, while in each timeseries, the data points are ordered by the timestamp. (Or, totally ordered by timestamp for all timeseries) 2. Join all time series that belong to the same device on the timestamp, in Relational SQL, looks like d1.s1 join d1.s2 on d1.s1.time=d1.s2.time join d1.s3 on d1.s1.time=d1.s3.time ... 3. Join all the time series in the database, which is what IoTDB now supports. This issue IOTDB-305 is for solving the 2nd query. Best, ----------------------------------- Xiangdong Huang School of Software, Tsinghua University 黄向东 清华大学 软件学院 Lei Rui <[email protected]> 于2019年11月23日周六 下午12:02写道： > Hi Tsai, > > > +1 for your idea. It sounds good to me. > > > Best, > Lei Rui > On 11/23/2019 09:42，Jack Tsai<[email protected]> wrote： > Hi all, > > I am recently working on this issue: > https://issues.apache.org/jira/browse/IOTDB-305, which is about resolving > the problem while users want to query something like below as the issue > reporter Lei Rui said: > > select * from root.sg.d1,root.sg.d2 where s1=1 <device separate>(a demo > conception) > / select * from root.sg.* where s1=1 <device separate>(a demo conception) > > There is no specific sql that could satisfy this kind of query > requirement. The only one which is similar to this concept is using the > “group by device” statement. However, it also cannot return the appropriate > result the users need as what Lei Rui mentioned in the issue. > > Now, I plan to edit the implement logic of the “group by device” > statement. The original implement method, which is like using the “and” > statement to form the condition part of the sql as mentioned in this issue, > cannot well suited for regular users’ requirements. > > In conclusion, the original function of the “group by device” will be > abandoned, and it will be replaced by the one which mentioned in this issue > to satisfy users query. I’m not sure whether this is OK for you guys or the > project. So if you got any advice, please welcome to discuss with me. > > Best regards, > Jack Tsai >
