Hi, >【select s1 as column1 from root.sg.d1, root.sg.d2 align by device】 also throw exception.
It can be supported actually, the result will be like: | Time | Device | column1 | | .... | root.sg.d1 | value1 | | .... | root.sg.d1 | value... | | .... | root.sg.d2 | value1 | | .... | root.sg.d2 | value... | But [select * as column1 from root.sg.d1 align by device], while * -> s1, s2 will throw an exception. > There are some examples that should be supported with alias. Thanks for the examples. Jialin Qiao <[email protected]> 于2020年8月14日周五 下午2:28写道： > Hi, > > > but it should be supported in raw data query too. > > +1 > > It seems that the "align by device query" has no advantages when using > alias. E.g., 【select s1 as column1 from root.sg.d1, root.sg.d2 align by > device】 also throw exception. > > Therefore, we should restrict that the from clause only has one prefix > path. > > For our query sql, it can be seen as: 【select suffixPath1 as alias1, > suffixPath2 as alias2, ... from prefixPath】 > > The raw paths are: > prefixPath.suffixPath1 -> alias1 > prefixPath.suffixPath2 -> alias2 > ... > > Then we need to check whether the prefixPath.suffixPath matches one series. > > There are some examples that should be supported with alias: > > select d1.s1 as column1 from root.sg > select * as column1 from root.sg.d1 > select count(s1) as column1 from root.sg.d1 > select count(s1) as column1 from root.sg.d1 group by (xxx) fill(xxx) > > 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: "Xiangwei Wei" <[email protected]> > > 发送时间: 2020-08-13 21:21:03 (星期四) > > 收件人: [email protected] > > 抄送: > > 主题: Re: [New feature] Add the alias and show it as column name when > querying > > > > Hi Xiangdong, > > > > > if only one time series can be matched that starts with "root.sg" and > > ends with "s1", it is ok,otherwise throw an exception. > > > > You are right, thanks for the illustration. > > > > > > > But for queries like "select s1 from root.sg.* align by device", the > > cases you mentioned will never happen, which is more graceful. > > > > I agree with the point you mentioned. This new feature is more suitable > for > > align by device query, but it should be supported in raw data query too. > > > > Xiangdong Huang <[email protected]> 于2020年8月13日周四 下午5:29写道： > > > > > Hi, > > > > > > > So we have to request that *every alias input by users is matching > one > > > time > > > series exactly.* > > > > > > for a query like `select s1 from root.sg.*`, if only one time series > can > > > be matched that starts with "root.sg" and ends with "s1", it is ok, > > > otherwise throw an exception. > > > It is fine... > > > > > > But for queries like "select s1 from root.sg.* align by device", the > cases > > > you mentioned will never happen, which is more graceful. > > > > > > So, maybe this feature is more suitable for such kind of queries. > > > > > > Best, > > > ----------------------------------- > > > Xiangdong Huang > > > School of Software, Tsinghua University > > > > > > 黄向东 > > > 清华大学 软件学院 > > > > > > > > > Xiangwei Wei <[email protected]> 于2020年8月13日周四 下午2:46写道： > > > > > > > Hi, > > > > > > > > I'm prepared to add a new feature in IoTDB as follows: > > > > > > > > Currently, when doing a query like *`select s1 from root.sg.d1`*, the > > > > result shows like: > > > > > > > > | Time | root.sg.d1.s1| > > > > | ... | ... | > > > > > > > > The column name *includes all prefix paths which are complex* and > seem > > > > inflexible and inconvenient in some situations. > > > > > > > > Therefore, I think we can add a new feature by adding the alias of > time > > > > series, which is like a relational database. For example, *`select > s1 as > > > > d1_temperature form root.sg.d1`* > > > > > > > > The result will be like: > > > > > > > > | Time | d1_temperature | > > > > | ... | .... | > > > > > > > > > > > > However, the new feature may be *limited* in IoTDB as a time series > > > > database. > > > > Because it's not matching one time series for one suffix path > exactly in > > > > SELECT Clause. For example, `select s1 as temperature from root.sg`. > If > > > > two > > > > devices d1 and d2 exist in root.sg, then they can't both be > temperature. > > > > We > > > > have to throw an exception here. > > > > > > > > So we have to request that *every alias input by users is matching > one > > > time > > > > series exactly.* > > > > > > > > > > > > Any suggestions or questions are welcome! Thank you! > > > > > > > > > > > > > > > > -- > > > > Best, > > > > Xiangwei Wei > > > > > > > > > > > > > -- > > Best, > > Xiangwei Wei > -- Best, Xiangwei Wei
