Hi Leo, "Extended column" is a special measure, which is to store a dimension value as a measure. It doesn't support aggregation, so if there are multiple values in this "measure", it will be empty.
Let me give an example. Say you have a table, which has dimensions like "*user_id*", "*user_name*", "*age*"; Here the "*user_id*" is unique, which will be used to do filtering/searching; The "user_name" will not be used for filtering, but it is nice to show the value in the result. So, in this case, we can declare "user_id" and "age" as dimensions, but define "user_name" as an extended column. Then the cube will have 2 dimensions instead of 3, its size will be smaller. When you run a query like "select user_id, user_name, count(*) from fact_table group by user_id, user_name", it will be expected, because the "user_name" value is decided (明确的) under the context of a "user_id"; But if you run a query without "user_id", for example, "select age, user_name, count(*) from fact_table group by age, user_name", this column will be empty, because it has no "user_id" in the row. The extended column can not work in the query independently So, the conclusion is, the extended column(s) need to appear together with its "host" column. If its "host" column is absent, the value will be empty. We will add this to Kylin document. Francis Liang <[email protected]> 于2018年11月5日周一 下午5:21写道： > Actually you need at least one aggregation, such as sum(lost_day_cnt), or > you may try select a, b from table group by a, b, which should not be the > normal case however. Hope this makes sense. Best, Feng. > > > > *发件人: *宋海涛 <[email protected]> > *发送时间: *2018年11月5日 17:16 > *收件人: *[email protected] > *主题: *答复: Extend Column Is Empty > > > > select zone, data_from,ent_name,org_no, org_name, goods_id,goods_spec, > big_mc,mid_mc,sma_mc,mini_mc,lost_day_cnt, > > lost_amt,avg_paid_in_amt,dt > > from gjst.st_goods_lost_monitor_detail_day where dt='20181102' and > > zone='西南平台' and data_from='haitang' and org_no='16208' > > > > *发件人:* Francis Liang [mailto:[email protected]] > *发送时间:* 2018年11月5日 17:14 > *收件人:* [email protected] > *主题:* 答复: Extend Column Is Empty > > > > Could you share your sql statement? Thanks. Best, Feng. > > > > *发件人**:* 宋海涛 <[email protected]> > *发送时间**:* Monday, November 5, 2018 4:58:53 PM > *收件人**:* [email protected] > *主题**:* Extend Column Is Empty > > > > Hi guys, > > > > When I run a SQL which contains extended columns, I got empty > values for extended columns . Anyone knows why? > > For example , ENT_NAME and ORG_NAME are extended column based on DATA_FROM > and ORG_NO: > > [image: cid:[email protected]] > > > > Thanks a lot. > > > > Leo > > > -- Best regards, Shaofeng Shi 史少锋
