如何让orientDB避免空值 [英] How to make orientDB avoid null

问题描述

当我执行下面的代码时，

When I execute code below,

select expand(distinct(@rid)) from (
  select from V
  where @rid = 'number not exist'
)

它返回

OCommandExecutionException:
     expression item '@rid' cannot be resolved because current record is NULL

这个内部选择只是为了测试，它不返回任何记录.

This inside select is just for test and it returns no record.

如果 select 没有返回记录，我希望返回 null和 expand(distinct(@rid)) 如果选择返回一些 @rid.

I want null to be returned if select returns no record and expand(distinct(@rid)) if select returns some @rid.

环境是 OrientDB 2.1.5，它发生在控制台和工作室.

The environment is OrientDB 2.1.5 and it occurs both in console and studio.

谢谢！

推荐答案

您的查询在 2.1.7 版中正常工作:

Your query works correctly in version 2.1.7:

OrientDB console v.2.1.7-SNAPSHOT (build 4) www.orientdb.com
...
orientdb> connect ...

orientdb {db=demo}> select expand(distinct(@rid)) from (select from V where @rid = 'number not exist')

0 item(s) found. Query executed in 0.076 sec(s).

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