如何从DolphinDB数据库的分区表中选择多个不同的列

Question

我在DolphinDB数据库中有一个分区表。其中两列是符号和名称。每个符号对应一个唯一的名称。我需要从分区表中选择不同的符号和名称。

我使用了以下脚本

t0 = select distinct(Symbol) as Symbol from t order by Symbol
t0 = select Symbol, Name from lj(t0, t, `Symbol)

但收到以下错误消息：

execution was completed with exception
A regular left table can't perform left join (lj), sorted left join (slj), full join (fj), asof join (aj), or window join (pwj, wj) with another distributed or segmented table.

Answer 1

对于您的情况，您可以通过平等联接来解决问题。在DolphinDB中，可以在常规表和分区表之间进行相等联接。

t0 = select distinct(Symbol) as Symbol from t order by Symbol
t0 = select Symbol, Name from ej(t0, t, `Symbol)
t0 = select * from t0 where prev(Symbol) ne Symbol